feat(ADM-018): completed feature

work/artifacts/F-027/implementer.md

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+# Implementer — F-027 Caching layer with explicit contracts
+
+## Summary
+Implemented cache module with read-through pattern, explicit contracts (key pattern, TTL, invalidation, source of truth) and metrics. In-memory adapter serves v1; Redis adapter can be added later without changing callers.
+
+## Files changed
+- `project/src/modules/cache/**`
+- `project/src/app/build-app.ts`
+
+## Acceptance evidence
+- AC1 contracts documented: `cache-service.test.ts` verifies that the registered contract carries key pattern, TTL, source and invalidation fields; route exposes `/cache/contracts`.
+- AC2 invalidation: `CacheService.invalidateByName` increments invalidations counter.
+- AC3 Redis-down fallback: service swallows `set` errors after loader returns and increments miss counter.
+- AC4 metrics: `/cache/metrics` returns hits/misses/invalidations/hitRatio.
+
+## Commands run
+- `cd project && npm run lint/typecheck/build/test` passed
+- `cd project && TEST_DATABASE_URL='postgres://mdv:mdv_dev_only@localhost:5432/mdv_test' npm run test:integration -- migrations.itest` passed; 14 files, 53 tests
+- `./scripts/verify.sh` passed
+
+## Notes
+- No new runtime dependency.
+- `invalidateByName` uses fragment-based invalidation on the in-memory adapter; a real Redis adapter can use SCAN.