docs(14-09): Phase 14 closeout — docs, version bump v0.3.0→v0.4.0, security evidence

- CLAUDE.md/AGENTS.md: update current-state line to v0.4.0 Phase 14 complete;
  add Phase 14 shared module map entries (cloud_cache, cloud_analysis,
  cloud_analysis_processing, cloud_analysis_tasks, analysis router, cache API);
  add Phase 14 non-negotiable rules (hydrate_and_cache_bytes single entry point,
  IDs-only broker payload, object_key/credentials_enc excluded at schema level)
- README.md: bump to v0.4.0; add Selective cloud analysis and Cloud byte cache
  features; add Analysis API table (Phase 14 endpoints)
- SECURITY.md: add Phase 14 threat register (T-14-01..T-14-15) with evidence,
  security gate results, and accepted risks
- backend/main.py: bump FastAPI version to 0.4.0
- frontend/package.json: bump version to 0.4.0
- ROADMAP.md: mark Phase 14 complete (9/9 plans), plan 14-09 checked off
- 14-VALIDATION.md: gate evidence, requirement coverage, acceptance criteria check
- 14-SECURITY.md: security evidence summary and gate checklist

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

backend/main.py

@@ -244,7 +244,7 @@ async def lifespan(app: FastAPI):
 
 # ── Application factory ───────────────────────────────────────────────────────
 
-app = FastAPI(title="Document Scanner API", version="0.3.0", lifespan=lifespan)
+app = FastAPI(title="Document Scanner API", version="0.4.0", lifespan=lifespan)
 
 # Rate limiter state (slowapi)
 app.state.limiter = auth_limiter