Harden security, fix rate-limiting, and rename proxy

- Move admin login lockout from client cookie to AppConfig (DB), keyed
  by hashed client IP — clearing browser cookies no longer bypasses it
- Replace rate-limit $transaction (TOCTOU) with atomic SQL
  INSERT...ON CONFLICT...RETURNING; add stale-entry cleanup on each
  submission to prevent table bloat
- Add 5 s module-level cache for middleware runtime state fetch, reducing
  per-request DB roundtrips
- Rename middleware.ts → proxy.ts to resolve Next.js 16 deprecation
  warning; update test import accordingly
- Require ADMIN_PASSWORD, ADMIN_AUTH_SECRET, ADMIN_BASIC_AUTH_USER, and
  ADMIN_BASIC_AUTH_PASS in docker-compose.yml (:? syntax) — startup
  fails loudly instead of using placeholder defaults
- Add set -e and informative echo lines to Dockerfile CMD for clearer
  startup failure attribution
- Export requireAdminAuth() from lib/admin-auth for centralised use in
  admin pages
- Add CLAUDE.md with architecture notes and working rules

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

Dockerfile

@@ -23,4 +23,4 @@ COPY --from=builder /app/next.config.mjs ./next.config.mjs
 
 EXPOSE 3000
 
-CMD ["/bin/sh", "-c", "mkdir -p /app/public/uploads/media && npm run db:migrate && npm run start -- --hostname 0.0.0.0 --port 3000"]
+CMD ["/bin/sh", "-c", "set -e; mkdir -p /app/public/uploads/media && echo '[startup] Running database migrations...' && npm run db:migrate && echo '[startup] Migrations complete. Starting server...' && npm run start -- --hostname 0.0.0.0 --port 3000"]