feat: SaaS foundation for CrowdSight

Elevate MiroFish/CrowdSight from single-container dev to a SaaS foundation:

- Local memory backend (Zep-compatible): memory services/models, local graph
  builder + updater, AgentActivity seam, import-boundary isolation; Zep stays
  default, local is opt-in behind MEMORY_BACKEND. Semantic parity not yet proven.
- Durable product persistence: projects/simulations/reports schema (migration
  0007) + tenant/owner-scoped ProductRepository + dual-write + scoped_project
  read-first + ArtifactStore abstraction; durable JobQueue + worker.py.
- SaaS hardening: durable RateLimiter (wired to login), UsageService (LLM
  accounting), redacted AuditService, idempotency, CORS allowlist, safe API
  errors, single-use PasswordResetService + endpoints (covers invite-pending).
- Exactly 3 roles (super_admin/admin/user) with tenant authz policy.
- Admin UI: GET/POST/PATCH /api/admin/users + GET/PUT /api/admin/settings
  (super-admin only, encrypted/masked); AdminView.vue + SettingsView.vue with
  admin/super-admin route guards, th/en i18n.
- Production deploy topology: multi-stage Dockerfile (frontend build + gunicorn
  wsgi + nginx SPA-proxy + supervisord worker), backend/wsgi.py, gunicorn dep.

Backend 197 passed; frontend 10 tests + build green. ruff unavailable (gap).
No commit of credentials; secrets handled via env/.env.example.
Deferred: Zep semantic A/B parity, object storage cutover, mobile QA, EasyPanel
container build of deploy topology.

backend/tests/test_api_errors.py

@@ -0,0 +1,48 @@
+import importlib.util
+from pathlib import Path
+import sys
+import unittest
+
+
+_MODULE_PATH = Path(__file__).parents[1] / "app" / "utils" / "api_errors.py"
+_SPEC = importlib.util.spec_from_file_location("api_errors_under_test", _MODULE_PATH)
+assert _SPEC is not None and _SPEC.loader is not None
+_MODULE = importlib.util.module_from_spec(_SPEC)
+sys.modules[_SPEC.name] = _MODULE
+_SPEC.loader.exec_module(_MODULE)
+
+ApiError = _MODULE.ApiError
+internal_error_payload = _MODULE.internal_error_payload
+
+
+class ApiErrorTests(unittest.TestCase):
+    def translator(self, key, **kwargs):
+        return f"{key}:{kwargs.get('id', '')}".rstrip(":")
+
+    def test_structured_error_has_code_and_localized_message_only(self):
+        error = ApiError(
+            code="project_not_found",
+            status_code=404,
+            message_key="api.projectNotFound",
+            params={"id": "demo"},
+        )
+        payload = error.to_payload(self.translator)
+        self.assertEqual(payload, {
+            "success": False,
+            "error_code": "project_not_found",
+            "message": "api.projectNotFound:demo",
+        })
+        self.assertNotIn("error", payload)
+        self.assertNotIn("details", payload)
+
+    def test_internal_error_never_contains_exception_text(self):
+        payload = internal_error_payload(self.translator)
+        self.assertEqual(payload["success"], False)
+        self.assertEqual(payload["error_code"], "internal_error")
+        self.assertEqual(payload["message"], "api.internalError")
+        self.assertNotIn("Traceback", str(payload))
+        self.assertNotIn("secret", str(payload))
+
+
+if __name__ == "__main__":
+    unittest.main()