Summary

• await MongoDB disconnect and Redis quit before exiting on SIGINT/SIGTERM
• make repeated/mixed signal handling idempotent
• settle and log cleanup failures without skipping the other cleanup or final exit
• add deterministic shutdown coordinator tests

Verification

• deno task check
• deno task test (35 passed)
• git diff --check

Fixes #660.

Summary by CodeRabbit

• Bug Fixes

  • Improved application shutdown handling to close database and cache connections before exiting.
  • Shutdown now continues safely when cleanup encounters errors.
  • Repeated shutdown signals no longer trigger duplicate cleanup operations.

• Tests

  • Added coverage for successful, repeated, and error-affected shutdown scenarios.

• Refactor

  • Standardized shutdown behavior across termination signals.