feat: real-time Socket.IO alert broadcasting system

[izzathnisfer]

Overview

This PR implements the real-time alert broadcasting system for the D2 Intelligence layer. It enables the backend to instantly notify connected clients (such as the D3 dashboard) when health anomalies are detected.

Key Changes

• Socket.IO Integration: Added an ASGI-compatible Socket.IO server within the FastAPI application.
• Real-time Broadcaster: Implemented a background Kafka consumer that listens to the alerts topic and broadcasts payloads to connected clients.
• Alert Filtering: Updated the alert endpoints to support optional patient_id filtering, ensuring patients only see relevant alerts.
• Observability: Added Prometheus counters to track alert delivery success and failure rates (d2_alerts_delivered_total, etc.).
• Testing: Added a comprehensive suite of unit and integration tests (21 tests total) covering the Socket.IO bridge, alert payload generation, and database interactions.

Verification Results

• Local Testing: All 21 tests passed successfully using pytest.
• CI/CD: Verified successful build and test execution in GitHub Actions (Run #79).
• Simulation: Verified functionality using the included scripts/simulate_alert.py script.

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[NadeeshaNJ]

Nice