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>

messages/de.json

@@ -145,7 +145,7 @@
     },
     "projects": {
       "eyebrow": "Ausgewaehlte Projekte",
-      "title": "Drei Beispiele fuer die Art von Arbeit, die ich gerne ausliefere.",
+      "title": "Hervorgehobene Projekte",
       "description": "Ausgewaehlte Projekte verbinden starke Interface-Qualitaet mit technischer Struktur, die auch nach dem Launch stabil bleibt.",
       "stackLabel": "Stack",
       "cta": "Projekt oeffnen",