Summary

• Add GitLab.com and self-managed GitLab personal snippets as a first-class provider, including provider selection, PAT login, CRUD, sync, search, task-list edits, and provider-aware links.
• Introduce a provider-neutral snippet API contract and bridge, with GitHub and GitLab owning their own request construction and response normalization.
• Scope credentials, cached account data, drafts, and async session state by provider/account, with migration and stale-session protection.
• Update settings, documentation, translations, packaging allowlists, and renderer/login fixtures for the new provider flow.

Validation

• npm run lint
• npm run test:unit — 352 tests across 58 files
• npm run test:smoke — login and authenticated renderer fixtures, including GitLab and multi-filter scenarios
• npm run test:packaged-smoke — packaged rendering and strict codesign verification
• git diff --check

Notes

• GitHub OAuth remains unchanged; GitLab authentication uses a personal access token.
• GitLab network behavior is covered with mocked provider and smoke tests. No live GitLab account or snippet data was mutated during validation.

Closes #262