refactor: engineering improvements -- API versioning, structured logging, Alembic, error standardization, test coverage

- API versioning: all REST endpoints prefixed with /api/v1/
- Structured logging: replaced stdlib logging with structlog (console/JSON modes)
- Alembic migrations: versioned DB schema with initial migration
- Error standardization: global exception handlers for consistent envelope format
- Interrupt cleanup: asyncio background task for expired interrupt removal
- Integration tests: +30 tests (analytics, replay, openapi, error, session APIs)
- Frontend tests: +57 tests (all components, pages, useWebSocket hook)
- Backend: 557 tests, 89.75% coverage | Frontend: 80 tests, 16 test files

docs/openapi-import-guide.md

@@ -86,7 +86,21 @@ Content-Type: application/json
 POST /api/openapi/jobs/{job_id}/approve
 ```
 
-No request body. Changes the job status to `approved`.
+No request body. Generates tool code for each classified endpoint and produces
+an agent YAML configuration. Response includes `generated_tools_count`.
+
+Response:
+```json
+{
+  "job_id": "abc123",
+  "status": "approved",
+  "spec_url": "https://api.example.com/openapi.yaml",
+  "total_endpoints": 5,
+  "classified_count": 5,
+  "error_message": null,
+  "generated_tools_count": 5
+}
+```
 
 ## Access Type Classification