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/worker.py

@@ -20,7 +20,7 @@ from app.core.logging import configure_logging, get_logger
 from app.db.session import SessionFactory
 from app.services import receipts as receipts_service
 from app.services.checkbox.client import CheckboxRateLimitedError, get_checkbox_client
-from app.services.crm.exo_client import ExoCrmClient
+from app.services.crm.client import get_crm_client
 from app.services.nova_poshta.np_client import NpTrackingClient
 from app.services.orders import sync_np_statuses
 
@@ -35,7 +35,7 @@ async def startup(ctx: dict[str, Any]) -> None:
     configure_logging()
     ctx["np_client"] = NpTrackingClient()
     ctx["checkbox_client"] = get_checkbox_client()
-    ctx["crm_client"] = ExoCrmClient(settings)
+    ctx["crm_client"] = get_crm_client()
     log.info("worker_starting", environment=settings.environment)