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>

docker-compose.yml

@@ -13,10 +13,10 @@ services:
       NEXT_PUBLIC_ADMIN_URL: ${NEXT_PUBLIC_ADMIN_URL:-https://root.mohfarawati.de}
       SITE_RUNTIME_ORIGIN: ${SITE_RUNTIME_ORIGIN:-http://127.0.0.1:3000}
       DATABASE_URL: postgresql://postgres:postgres@db:5432/moh_sass?schema=public
-      ADMIN_PASSWORD: ${ADMIN_PASSWORD:-change-me}
-      ADMIN_AUTH_SECRET: ${ADMIN_AUTH_SECRET:-change-me-long-secret}
-      ADMIN_BASIC_AUTH_USER: ${ADMIN_BASIC_AUTH_USER:-root}
-      ADMIN_BASIC_AUTH_PASS: ${ADMIN_BASIC_AUTH_PASS:-change-me-root}
+      ADMIN_PASSWORD: ${ADMIN_PASSWORD:?ADMIN_PASSWORD must be set in .env}
+      ADMIN_AUTH_SECRET: ${ADMIN_AUTH_SECRET:?ADMIN_AUTH_SECRET must be set in .env (use a long random string)}
+      ADMIN_BASIC_AUTH_USER: ${ADMIN_BASIC_AUTH_USER:?ADMIN_BASIC_AUTH_USER must be set in .env}
+      ADMIN_BASIC_AUTH_PASS: ${ADMIN_BASIC_AUTH_PASS:?ADMIN_BASIC_AUTH_PASS must be set in .env}
     depends_on:
       db:
         condition: service_healthy