feat: Implement Redis-to-PostGIS background worker and secure WebSockets

[GiZano]

Overview

This PR introduces the core asynchronous data persistence layer for the QuakeGuard backend, alongside critical security updates for the mobile application's real-time feeds.

Incoming IoT payloads validated by the FastAPI gateway are now reliably popped from the Redis message broker and batch-inserted into the PostGIS database via a dedicated Python background worker.

Changes Made

• Background Worker (Implement Background Worker for Redis-to-PostGIS Persistence #51): * Created src/worker.py with a continuous brpop loop listening to the seismic_events queue. (Create worker.py in the src/ directory. #55, Implement a continuous loop that reads from the Redis seismic_events queue. #56)
  • Safely mapped JSON payloads to the Misuration SQLAlchemy ORM, ensuring device_timestamp mismatches do not crash the insert. (Parse the JSON payload and execute an INSERT statement into the PostGIS measurements table. #57)
  • Implemented resilient error handling: failed database transactions are rolled back and the payload is routed to seismic_events_dlq for manual recovery. (Implement error handling (e.g., if PostGIS goes down, push the payload back to a Dead Letter Queue or retry). #58)
• WebSocket Security (Secure WebSocket Connections (Mobile Auth) #54): * Added token verification to the /ws/alerts endpoint. Connections without a valid MOBILE_WS_TOKEN are now rejected with WS_1008_POLICY_VIOLATION.
• Testing & Infrastructure Fixes:
  • Fixed a bug in tests/stress_test.py where a 1.5s sleep delay caused the load test to hang. Adjusted to 0.025s to properly simulate 40 req/sec and interact correctly with the Redis Rate Limiter.
  • Solved Docker Python buffering issues by configuring PYTHONUNBUFFERED=1 and forcing flush=True on worker logs for immediate visibility.

Testing Performed

• Sent 200 concurrent requests via stress_test.py (Phase 1).
• Verified Redis Rate Limiter correctly blocks overflow traffic (Status 429).
• Verified Bad Signature & Replay Attacks are blocked (Status 401/403).
• Confirmed the worker container spins up, connects to Redis/Postgres, and successfully transitions items from the Redis queue to the misuration table.

Related Issues

Closes #51
Closes #54
Closes #55
Closes #56
Closes #57
Closes #58