feat(ingestion): add health endpoints with publisher initialization retry

[Bafbi]

Summary

• Add /healthz/live and /healthz/ready endpoints to ingestion service
• Implement HealthService with exponential backoff retry for publisher initialization
• Add Docker healthcheck and restart policy to docker-compose

Changes

New Files

• services/ingestion/src/ingestion/api/v1/endpoints/health.py - Health endpoints
• services/ingestion/src/ingestion/services/health.py - HealthService with retry logic

Modified Files

• services/ingestion/src/ingestion/main.py - Add lifespan for startup init
• infra/local/docker-compose.yml - Add healthcheck configuration

Behavior

• /healthz/live returns {"status": "alive"} (always 200)
• /healthz/ready returns {"status": "ready", "publisher": "ok"} when publisher is initialized, 503 otherwise
• Publisher initialization retries in background with exponential backoff (1s → 2s → 4s → ... → 30s max)
• Docker healthcheck polls /healthz/ready every 10s