fix: address project review findings

Security and robustness:
- storage-agent rejects an empty INTERNAL_TOKEN (config notEmpty + middleware)
- api takes the client IP only from X-Real-IP (chi RealIP trusted True-Client-IP)
- /readyz reports ok/fail and logs the cause; checks run in parallel with a timeout
- storage-agent shuts down gracefully; shared httpx.NewServer/Serve with IdleTimeout
- goose migrations take a Postgres advisory lock
- recommender readyz: per-check timeout, redis socket timeouts

Clients:
- Android release allows cleartext HTTP for LAN servers (expo-build-properties)
- checkServer times out after 10s; connect button is disabled while checking

Deploy and CI:
- install.sh hands cache/uploads/updates/models to the non-root service users
- update.sh refuses downgrades unless PIPU_ALLOW_DOWNGRADE=1
- recommender/analyzer get only the env they need; required secrets fail fast
- nginx security headers and CSP; strip True-Client-IP
- dev compose binds ports to 127.0.0.1; postgres/redis images pinned
- version.mjs fails on a malformed explicit tag instead of releasing 0.0.0-dev
- contract check catches untracked generated files
- final releases fail without a release keystore; changelog skips rc tags

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/Dockerfile

@@ -13,6 +13,7 @@ RUN pnpm --filter @pipu/web build
 
 FROM nginx:1.28-alpine
 COPY deploy/nginx/default.conf.template /etc/nginx/templates/default.conf.template
+COPY deploy/nginx/security-headers.conf /etc/nginx/snippets/security-headers.conf
 COPY --from=build /repo/apps/web/dist /usr/share/nginx/html
 ARG VERSION=0.0.0-dev
 LABEL org.opencontainers.image.version=${VERSION}