chore: complete v1.0 Analytics & Monitoring milestone

Archive milestone artifacts (roadmap, requirements, audit, phase directories)
to .planning/milestones/. Evolve PROJECT.md with validated requirements and
decision outcomes. Create MILESTONES.md and RETROSPECTIVE.md.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.planning/milestones/v1.0-phases/02-backend-services/02-04-SUMMARY.md

@@ -0,0 +1,101 @@
+---
+phase: 02-backend-services
+plan: 04
+subsystem: infra
+tags: [firebase-functions, cloud-scheduler, health-probes, retention-cleanup, onSchedule]
+
+# Dependency graph
+requires:
+  - phase: 02-backend-services
+    provides: healthProbeService.runAllProbes(), alertService.evaluateAndAlert(), HealthCheckModel.deleteOlderThan(), AlertEventModel.deleteOlderThan(), deleteProcessingEventsOlderThan()
+provides:
+  - runHealthProbes Cloud Function export (every 5 minutes, separate from processDocumentJobs)
+  - runRetentionCleanup Cloud Function export (weekly Monday 02:00, 30-day rolling deletion)
+affects: [03-api-layer, 04-frontend, phase-03, phase-04]
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "onSchedule Cloud Functions use dynamic import() to avoid cold-start overhead and module-level secret access"
+    - "Health probes as separate named Cloud Function — never piggybacked on processDocumentJobs (PITFALL-2)"
+    - "retryCount: 0 for health probes — 5-minute schedule makes retries unnecessary"
+    - "Promise.all() for parallel multi-table retention cleanup"
+
+key-files:
+  created: []
+  modified:
+    - backend/src/index.ts
+
+key-decisions:
+  - "runHealthProbes is completely separate from processDocumentJobs — distinct Cloud Function, distinct schedule (PITFALL-2 compliance)"
+  - "retryCount: 0 on runHealthProbes — probes recur every 5 minutes, retry would create confusing duplicate results"
+  - "runRetentionCleanup uses Promise.all() for parallel deletes — three tables are independent, no ordering constraint"
+  - "runRetentionCleanup only deletes monitoring tables (service_health_checks, alert_events, document_processing_events) — agentic RAG tables out of scope per research Open Question 4"
+  - "RETENTION_DAYS = 30 is a constant, not configurable — matches INFR-03 spec exactly"
+
+patterns-established:
+  - "Scheduled Cloud Functions: dynamic import() + explicit secrets array per function"
+  - "Retention cleanup: Promise.all([model.deleteOlderThan(), ...]) pattern for parallel table cleanup"
+
+requirements-completed: [HLTH-03, INFR-03]
+
+# Metrics
+duration: 1min
+completed: 2026-02-24
+---
+
+# Phase 2 Plan 04: Scheduled Cloud Function Exports Summary
+
+**Two new Firebase onSchedule Cloud Functions: runHealthProbes (5-minute interval) and runRetentionCleanup (weekly Monday 02:00) added to index.ts as standalone exports decoupled from document processing**
+
+## Performance
+
+- **Duration:** ~1 min
+- **Started:** 2026-02-24T19:34:20Z
+- **Completed:** 2026-02-24T19:35:17Z
+- **Tasks:** 2
+- **Files modified:** 1
+
+## Accomplishments
+- Added `runHealthProbes` onSchedule export that calls `healthProbeService.runAllProbes()` then `alertService.evaluateAndAlert()` on a 5-minute cadence
+- Added `runRetentionCleanup` onSchedule export that deletes rows older than 30 days from `service_health_checks`, `alert_events`, and `document_processing_events` in parallel
+- Both functions use dynamic `import()` pattern and list all required Firebase secrets explicitly
+- All 64 existing tests continue to pass
+
+## Task Commits
+
+Both tasks modified the same file in a single edit operation:
+
+1. **Task 1: Add runHealthProbes** - `1f9df62` (feat) — includes both Task 1 and Task 2
+2. **Task 2: Add runRetentionCleanup** — included in `1f9df62` above
+
+**Plan metadata:** (docs commit forthcoming)
+
+## Files Created/Modified
+- `backend/src/index.ts` - Added `runHealthProbes` and `runRetentionCleanup` scheduled Cloud Function exports after `processDocumentJobs`
+
+## Decisions Made
+- Combined both exports into one commit since they were added simultaneously to the same file — functionally equivalent to two separate commits
+- `retryCount: 0` on `runHealthProbes` — with a 5-minute schedule, a failed probe run is superseded by the next run before any retry would be useful
+- `timeoutSeconds: 120` on `runRetentionCleanup` — cleanup may process large batches; 60 seconds could be tight for large datasets
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+None — TypeScript compiled cleanly on first pass, all tests passed.
+
+## User Setup Required
+None - no external service configuration required. Firebase deployment will pick up the new exports automatically.
+
+## Next Phase Readiness
+- All Phase 2 backend service plans complete (02-01 through 02-04)
+- Ready for Phase 3 API layer development
+- Health probe infrastructure fully wired: probes run on schedule, alerts sent via email, data retained for 30 days
+- Monitoring system is operational end-to-end
+
+---
+*Phase: 02-backend-services*
+*Completed: 2026-02-24*