fix(prod): harden production configuration for launch

- Gate Swagger/ReDoc/OpenAPI behind DEBUG (no public API schema in prod)
- Sentry send_default_pii only in dev (no auth headers/bodies in events)
- Remove alembic from Dockerfile CMD (releaseCommand owns migrations; CMD copy raced across replicas/restarts)
- Decouple rate limiting from DEBUG via RATE_LIMIT_ENABLED (PR envs with DEBUG=true were unlimited); tests disable the live limiter in conftest
- max_instances=1 on the 4 scheduler jobs missing it
- Boot-time failure when SELF_SERVE_ENABLED without RESEND_API_KEY/ANTHROPIC_API_KEY/FRONTEND_URL
- Reject localhost OAUTH_REDIRECT_BASE outside DEBUG
- pool_pre_ping + pool_recycle on the app engine
- Frontend: DEV-gate stale-async console.warn; document VITE_SELF_SERVE_ENABLED fallback semantics in Dockerfile

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/conftest.py

@@ -29,6 +29,12 @@ from app import models as _models  # noqa: F401
 # Disable invite code requirement for tests
 settings.REQUIRE_INVITE_CODE = False
 
+# Disable rate limiting in tests — auth-heavy suites would trip the
+# per-minute login/register limits. The limiter is constructed at import
+# time, so flip the live instance rather than the setting.
+from app.core.rate_limit import limiter as _limiter  # noqa: E402
+_limiter.enabled = False
+
 # Test database URL — NEVER reuse DATABASE_URL. The test_db fixture does
 # `DROP SCHEMA public CASCADE` on every test; if DATABASE_URL (which normally
 # points at the dev/prod DB) leaked into this value, running `pytest tests/`