feat(routes-f): implement stubs for #336 #327 #328 #309

[josephchimebuka]

Closes #336
Closes #327
Closes #328
Closes #309

Summary

This PR delivers 4 backend routes-f stubs in one branch:

• Backend: Add routes-f circuit breaker stub #336 Add route-level circuit breaker stub for external dependency calls.
• Backend: Add routes-f signed upload URL endpoint #327 Add signed upload URL generation endpoint (stub).
• Backend: Add routes-f daily activity aggregation endpoint #328 Add daily activity aggregation endpoint.
• Backend: Add routes-f dependency health endpoint #309 Add dependency health check endpoint (stub).

What Changed

• Added in-memory deterministic circuit breaker with per-key failure tracking and state transitions:
  • closed -> open at threshold
  • auto open -> half-open after cooldown
  • half-open -> closed on success, half-open -> open on failure
• Added POST /api/routes-f/uploads/sign:
  • validates file metadata (fileName, fileType, fileSize)
  • enforces allowed MIME types and max size
  • returns fake signed URL response { url, expiresAt, method }
• Added GET /api/routes-f/activity/daily?days=:
  • defaults to last 7 days when missing/invalid
  • enforces upper bound for requested days
  • returns total count and per-day buckets from mock data
• Added GET /api/routes-f/deps:
  • returns stable typed dependency payload when healthy
  • uses route-level circuit breaker around dependency checks
  • returns short-circuit response with retry hint when breaker is open

Files Added

• lib/routes-f/circuit-breaker.ts
• lib/routes-f/activity.ts
• lib/routes-f/deps.ts
• app/api/routes-f/uploads/sign/route.ts
• app/api/routes-f/activity/daily/route.ts
• app/api/routes-f/deps/route.ts
• lib/routes-f/__tests__/circuit-breaker.test.ts
• app/api/routes-f/__tests__/uploads-sign.test.ts
• app/api/routes-f/__tests__/activity-daily.test.ts
• app/api/routes-f/__tests__/deps.test.ts

Acceptance Criteria Mapping

• Backend: Add routes-f circuit breaker stub #336:
  • consecutive failures tracked per dependency key
  • breaker opens at threshold, short-circuits while open
  • auto half-open after cooldown
  • short-circuit response includes retryAfterSeconds
  • tests cover closed/open/half-open transitions
• Backend: Add routes-f signed upload URL endpoint #327:
  • endpoint accepts metadata and validates
  • invalid metadata returns 400
  • response includes url, expiresAt, method
  • tests cover validation and response shape
• Backend: Add routes-f daily activity aggregation endpoint #328:
  • endpoint supports days query with default 7
  • max-day upper bound enforced
  • response includes total and daily buckets
  • tests cover bucket generation
• Backend: Add routes-f dependency health endpoint #309:
  • endpoint returns { healthy, deps } using fixed/stubbed checks
  • route is callable without auth
  • tests cover response shape

Validation

• Implemented and committed all new route + helper tests.
• Local Jest execution in this environment currently fails at startup with Bus error (core dumped) before suites run.
• Existing repo-wide TypeScript check also has pre-existing unrelated errors (e.g. missing type declarations for framer-motion / react-icons) not introduced by this PR.

Notes

• Circuit breaker is intentionally in-memory for now, per requirement.
• No cloud provider integration for signed URLs yet (stub response only).

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