Add CRM stub flag, deploy/backup scripts, CI and prod runbook

- CRM_USE_STUB: local runs no longer reach the live CRM. With only the
  Checkbox stub, a stub receipt would still move the real order to PACKED.
  Refused in production, same as CHECKBOX_USE_STUB.
- scripts/deploy.sh: backup, fast-forward main, build, health check and
  code rollback on failure. scripts/backup.sh: pg_dump with verification
  and 14-day rotation (used by cron and deploy.sh).
- Gitea Actions CI: ruff + pytest, oxlint + build.
- DEPLOY.md runbook; CLAUDE.md rules for safe local development.

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

backend/app/core/config.py

@@ -61,6 +61,9 @@ class Settings(BaseSettings):
     crm_secret_key: str = ""
     crm_shop_key: str = ""
     crm_sid: int = 1
+    # Стаб вместо реальной CRM: иначе локальный worker переводил бы боевые заказы
+    # в PACKED после стаб-чеков Checkbox. В проде запрещено.
+    crm_use_stub: bool = False
 
     # --- Nova Poshta ---
     # Ключи НП хранятся у касс (`cash_registers.np_api_key_enc`). Эта переменная