Add comprehensive structured logging with Loki + Grafana
Backend logging:
- Centralized JSON logging config with LOG_LEVEL env var
- Request logging middleware: user, method, path, status, duration, request_id
- Fixed all 9 silent except:pass blocks to log warnings with tracebacks
- Celery workers use same structured JSON format
Infrastructure:
- Loki 3.3.2 for log storage (30-day retention)
- Promtail 3.3.2 for Docker container log shipping
- Grafana 10.3.1 with auto-provisioned Loki datasource
- Grafana on port 3002 (admin/pedshub_grafana)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
d0518d0737