…cation pages (closes #314)

Introduces the Archera Insurance CTA at the two high-intent moments
where a user is about to commit money, plus two education pages that
explain what Archera Insurance is and how the integration works.

**New module — frontend/src/archera.ts**
- `renderArcheraCTA()`: returns a small, muted <p> with an inline
  <button> that reads "Worried about committing? Archera Insurance
  underwrites commitment-overuse — learn how it works →". Placed
  below the approval note in the Purchase modal, and before the
  Save/Cancel row in Plan-creation modals.
- `openArcheraPage('what-is-archera' | 'how-it-works')`: renders a
  full-viewport overlay panel using DOM methods only (no innerHTML).
  Doesn't touch SPA routing state or the URL.
- `closeArcheraPage()`: hides + clears the overlay.
- `ARCHERA_SIGNUP_URL = 'https://archera.ai/signup?mode=cudly'` for
  attribution-tagged referral links.

**Page A — "What is Archera Insurance?"**
Plain-language explainer: commitment-overuse insurance, how Archera
earns (sharing-of-savings), when it makes sense, what CUDly's role is.
Cross-links to Page B. Signup link at bottom (target=_blank,
rel="noopener noreferrer").

**Page B — "How the CUDly ↔ Archera integration works"**
Step-by-step: sign up → Archera generates pre-filled IaC for AWS/GCP
(or OAuth consent for Azure) → Archera ingests cost data → purchase
commitments normally through CUDly. Disclaimers: Archera is
third-party, no credentials stored in CUDly. Cross-links to Page A.
Signup link at bottom.

TODO(@cristim) markers flag all copy that needs final review.

**Modal integration**
- `recommendations.ts / openPurchaseModal`: appends `renderArcheraCTA()`
  inside `#purchase-details`, below the approval note.
- `plans.ts / openCreatePlanModal + openNewPlanModal`: calls
  `injectPlanModalCTA()` (guarded against duplication with an id
  check) to insert the CTA before `.modal-buttons` in `#plan-form`.

**CSS (styles/modals.css)**: `.archera-cta`, `.archera-cta-link`,
`#archera-page-container`, `.archera-page-inner`, `.archera-page-back`,
`.archera-signup-block`, `.archera-signup-btn`, `.archera-signup-note`.

**HTML (index.html)**: adds `<div id="archera-page-container"
role="region" aria-label="Archera Insurance information">` (hidden
by default) before the modal stack.

**Tests (archera.test.ts)**: 26 assertions covering renderArcheraCTA
structure, page A/B content + crosslinks + signup link attributes,
closeArcheraPage, and CTA injection in both Purchase and Plan modals.

Nothing in backend/, cmd/, internal/, iac/, terraform/, or scripts/ is
touched. This is a frontend-only change. Supersedes PR #310 and PR #315
(closed without merging; earlier iterations bundled IAM/IaC which was
rejected by Archera-side review — see issue #314 for history).

…es + email mentions (closes #314) (#336)

* feat(frontend): Archera Insurance CTA in purchase + plan modals + education pages (closes #314)

Introduces the Archera Insurance CTA at the two high-intent moments
where a user is about to commit money, plus two education pages that
explain what Archera Insurance is and how the integration works.

**New module — frontend/src/archera.ts**
- `renderArcheraCTA()`: returns a small, muted <p> with an inline
  <button> that reads "Worried about committing? Archera Insurance
  underwrites commitment-overuse — learn how it works →". Placed
  below the approval note in the Purchase modal, and before the
  Save/Cancel row in Plan-creation modals.
- `openArcheraPage('what-is-archera' | 'how-it-works')`: renders a
  full-viewport overlay panel using DOM methods only (no innerHTML).
  Doesn't touch SPA routing state or the URL.
- `closeArcheraPage()`: hides + clears the overlay.
- `ARCHERA_SIGNUP_URL = 'https://archera.ai/signup?mode=cudly'` for
  attribution-tagged referral links.

**Page A — "What is Archera Insurance?"**
Plain-language explainer: commitment-overuse insurance, how Archera
earns (sharing-of-savings), when it makes sense, what CUDly's role is.
Cross-links to Page B. Signup link at bottom (target=_blank,
rel="noopener noreferrer").

**Page B — "How the CUDly ↔ Archera integration works"**
Step-by-step: sign up → Archera generates pre-filled IaC for AWS/GCP
(or OAuth consent for Azure) → Archera ingests cost data → purchase
commitments normally through CUDly. Disclaimers: Archera is
third-party, no credentials stored in CUDly. Cross-links to Page A.
Signup link at bottom.

TODO(@cristim) markers flag all copy that needs final review.

**Modal integration**
- `recommendations.ts / openPurchaseModal`: appends `renderArcheraCTA()`
  inside `#purchase-details`, below the approval note.
- `plans.ts / openCreatePlanModal + openNewPlanModal`: calls
  `injectPlanModalCTA()` (guarded against duplication with an id
  check) to insert the CTA before `.modal-buttons` in `#plan-form`.

**CSS (styles/modals.css)**: `.archera-cta`, `.archera-cta-link`,
`#archera-page-container`, `.archera-page-inner`, `.archera-page-back`,
`.archera-signup-block`, `.archera-signup-btn`, `.archera-signup-note`.

**HTML (index.html)**: adds `<div id="archera-page-container"
role="region" aria-label="Archera Insurance information">` (hidden
by default) before the modal stack.

**Tests (archera.test.ts)**: 26 assertions covering renderArcheraCTA
structure, page A/B content + crosslinks + signup link attributes,
closeArcheraPage, and CTA injection in both Purchase and Plan modals.

Nothing in backend/, cmd/, internal/, iac/, terraform/, or scripts/ is
touched. This is a frontend-only change. Supersedes PR #310 and PR #315
(closed without merging; earlier iterations bundled IAM/IaC which was
rejected by Archera-side review — see issue #314 for history).

* feat(frontend,email): address CR findings + scope additions (issue #314)

Frontend (CR fixes):
- archera.ts: save/restore focus around overlay open/close (CR: focus
  restoration on closeArcheraPage)
- modals.css: raise #archera-page-container z-index from 900 to 1100
  so overlay sits above .modal layers (CR: z-index below modals)
- archera.test.ts: add global afterEach DOM teardown to prevent stale-
  node collisions between test suites (CR: missing teardown)

Frontend (scope additions from coordinator):
- archera.ts: update renderArcheraCTA copy to "Insure this commitment/
  plan with Archera →"; add transparency disclosure section (Page A:
  "Why is CUDly telling me about this?", Page B: "Disclosure") carrying
  two non-negotiable facts: CUDly fully functional without Archera +
  Archera sponsors CUDly; add handleArcheraDeeplink() for deep-link
  routing from email; export ARCHERA_PAGE_A/B_PATH constants
- app.ts: wire handleArcheraDeeplink() into init() after
  handlePurchaseDeeplink()
- plans.ts: pass 'plan' context to renderArcheraCTA in injectPlanModalCTA
- archera.test.ts: update CTA copy assertions; add disclosure tests (6);
  add handleArcheraDeeplink tests (3); total: 41 tests, all passing

Backend (email templates — scope addition):
- sender.go: add ArcheraEducationURL field to NotificationData; empty
  value silently omits the Archera block for backward compat
- templates.go: add conditional Archera 7-day enrollment block to
  purchaseApprovalRequestTemplate (plain-text), purchaseApprovalRequest-
  HTMLTemplate (HTML), and purchaseConfirmationTemplate
- handler_purchases.go, execution.go: populate ArcheraEducationURL as
  DashboardURL + "/archera-insurance" matching ARCHERA_PAGE_A_PATH
- template_renderers_test.go: add 4 Go tests asserting Archera content
  in all three modified templates + absence test when URL is empty

* refactor(api): extract archeraEducationURL helper to reduce sendPurchaseApprovalEmail cyclomatic complexity

The if dashboardBase != "" guard added in the previous commit pushed
sendPurchaseApprovalEmail from complexity 10 to 11, exceeding the
gocyclo pre-commit threshold. Extracted the guard into a package-private
archeraEducationURL helper; sendPurchaseApprovalEmail calls it inline
without a branch, restoring complexity to 10.

* refactor(archera): post-action offer modal + single education page

Restructures the Archera Insurance flow into a post-action offer modal,
collapses the previously split education pages into one, and tightens
the copy.

Frontend changes:
- Replace the inline "Insure this {commitment,plan} with Archera →" CTA
  inside the Purchase and Plan-creation modals with a new post-action
  offer modal (openArcheraOfferModal). The modal pops after a successful
  Send-for-Approval submission (app.ts handleExecutePurchase +
  handleFanOutExecute) or plan creation (plans.ts savePlan). The user
  sees title + lead + brief disclosure, then a collapsed "Learn more"
  drop-down, then two equal-weight actions: "No thanks" and "Sign up at
  Archera →" (opens archera.ai in a new tab).
- Merge the previously separate "What is Archera Insurance?" (Page A)
  and "How the integration works" (Page B) overlays into a single
  education page (buildArcheraPage). Both ARCHERA_PAGE_A_PATH and
  ARCHERA_PAGE_B_PATH still deep-link to the merged page (PAGE_B kept
  for backward compatibility with already-delivered email links).
- "Learn more" is a native <details>/<summary> that expands the full
  education content inline within the offer modal. Summary text on the
  left, chevron on the right (rotates on open). Body inherits .archera-
  page-inner typography for visual parity with the standalone page.
- Education content tightened: dedupe the lead-paragraph + "Why is CUDly
  telling me about this?" overlap, drop the four-bullet Disclaimers
  section in favour of a single closing "Full disclosure:" paragraph
  that absorbs the legal/scope points. Drop the "All Upfront" qualifier
  from "When it makes sense" and reframe the second use case from
  "finance team requires a safety net" to user-perspective "you want to
  be covered in case your usage drops".
- "How it works" intro now explicitly states the 7-day enrollment
  window from each purchase.
- Premium note clarifies the insurance fee is paid to Archera and the
  cloud commitment bought through CUDly is unaffected (same price,
  same billing) — replaces the earlier sharing-of-savings framing.
- Add aria-haspopup="dialog" + aria-expanded toggling on the (now-
  removed) Columns popover trigger to expose dialog state to assistive
  tech. (No-op for the removed inline CTAs; this change is the modal's
  a11y surface.)
- Drop the inline scripts' em-dashes from JSDoc + user-facing strings.

Tests:
- archera.test.ts rewritten: drops renderArcheraCTA + page A/B + plan-
  modal-CTA + purchase-modal-CTA describe blocks (those surfaces are
  gone). Adds openArcheraOfferModal describes covering visibility,
  context-dependent headlines, signup link attributes, No-thanks +
  backdrop + ESC close, Learn-more collapsible expand, re-open replace
  semantics. handleArcheraDeeplink test now verifies both legacy and
  current URL paths open the same merged page. 1605 frontend tests
  pass.

* feat(email): inline expanded Archera section in approval + confirmation

Replaces the 4-line "Learn more: <URL>" Archera block in the purchase-
confirmation, purchase-approval-request (plain text), and approval-
request (HTML) emails with the full education content inlined into
the message body — so recipients don't need to click through to the
dashboard to read what the option is, when it makes sense, and how
it works.

Structure mirrors the in-app offer modal's expanded "Learn more"
content:
  - Header + 7-day enrollment window note
  - One-paragraph lead (covers the gap + non-gating)
  - "When it makes sense" (2 use cases)
  - "How it works" with the 3-step onboarding flow
  - Premium clarification (insurance fee is separate from the cloud
    commitment; same price, same billing)
  - Full-disclosure paragraph (sponsorship + scope + Archera-owns-terms)
  - Sign up CTA + permalink

Always-expanded (no <details>/<summary>): Outlook desktop, Outlook.com,
and mobile Outlook strip those, so the safest is a flat inline body.
Apple Mail, iOS Mail, and Gmail web render the styled HTML naturally;
all other clients fall back to the plain-text version.

The original {{.ArcheraEducationURL}} is kept as a "Permalink:" at the
bottom of each block — preserves the existing tests' URL assertions
and gives a fallback for forwarded emails, bookmarks, or clients that
mangle the inlined HTML. 310 Go tests still pass.

* fix(frontend/archera): cleanup leaked listener + add focus trap to dialog

Address two CR findings on PR #336:

1. **Stale keydown listener leak**: openArcheraOfferModal added a
   document-level keydown handler (ESC closes) and stored its cleanup in
   `_offerModalCleanup` on every call, but didn't first invoke the prior
   cleanup. A re-open without an explicit close in between leaked the
   previous handler. Fix: call `_offerModalCleanup()` (if set) at the top
   of openArcheraOfferModal before attaching the new handler. Idempotent
   — no-op when no prior open is in flight.

2. **No focus trap on the dialog panel**: the panel declares
   `role="dialog" aria-modal="true"` but Tab / Shift+Tab let keyboard
   users escape into the background app. That's an a11y regression for
   an "aria-modal=true" element. Fix: attach a panel-level keydown
   handler that intercepts Tab — Tab on last focusable wraps to first,
   Shift+Tab on first wraps to last. Focusables are re-queried on each
   Tab press (not cached at modal-build time) so the Tab traversal
   picks up the additional focusables that the <details> drop-down
   expands when opened. Trap handler is torn down alongside the ESC
   handler by the merged `_offerModalCleanup` closure.

Tests in archera.test.ts:
- `re-opening tears down the previous open's ESC listener (no leak)`
  spies on document.addEventListener / removeEventListener and asserts
  the second open both adds AND removes one keydown handler.
- `traps Tab focus inside the panel (Tab from last → first)`
  focuses the last focusable, dispatches Tab, asserts focus wraps to
  the first and the event was preventDefaulted.
- `traps Shift+Tab focus inside the panel (Shift+Tab from first → last)`
  the mirror case.

1608 frontend tests pass (3 new).