fix(securitate): hardening prod — headere, body-cap, non-root, backup

Findings security-review P1/P2 (2026-07-03):
- headere de securitate pe toate raspunsurile (nosniff, X-Frame-Options,
  Referrer-Policy, HSTS doar pe HTTPS) + teste
- body-cap global 10MB ca middleware ASGI pur (413 inainte de parserul
  multipart/JSON; verificarea per-endpoint ramane strat 2)
- imagine Docker non-root (uid 10001), port 8010 aliniat, loguri pe
  volumul /data
- fail-fast la boot cu rar_env=prod fara AUTOPASS_REQUIRE_API_KEY sau
  AUTOPASS_SESSION_SECRET
- compose: env-uri critice obligatorii (:?) ca api/worker sa nu diverga
  tacit; FORWARDED_ALLOW_IPS ca rate-limit-ul sa vada IP-ul real dupa
  Traefik
- signup fara PII in stdout: log_event in loc de print cu email (idem
  notify degradat)
- ratelimit: sterge cheile fara timestamp-uri valide (crestere monotona
  a memoriei pe IP-uri reale)
- backup criptat SQLite (backup online API, gpg AES256) + verificare
  restore + docs/backup.md

Suita completa verde: 1557 passed, 1 skipped (live).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/web/auth_routes.py

@@ -15,6 +15,7 @@ from ..auth import create_api_key
 from ..config import get_settings
 from ..db import get_connection
 from ..email import notify_signup
+from ..observ import log_event
 from ..users import count_admins, create_user, list_admin_emails, verify_password
 from ..web.csrf import get_csrf_token, verify_csrf
 from ..web.ratelimit import check_rate_limit
@@ -157,7 +158,7 @@ async def signup_post(
         conn.close()
 
     set_session(request, account_id, user_id)
-    print(f"SIGNUP cont={account_id} email={email}", flush=True)
+    log_event("signup", account_id=account_id, mesaj="cont nou creat")
 
     # Notificare email admin (best-effort, nu blocheaza signup-ul)
     try: