docs: add unified logging system documentation and CI/CD integration (refs #87)

- Update staging workflow to use LOG_LEVEL=DEBUG
- Create docs/LOGGING.md with unified logging documentation
- Delete docs/UX-DEBUGGING.md (replaced by LOGGING.md)
- Update architecture to 9-container (6 app + 3 logging)
- Update CLAUDE.md, README.md, docs/README.md, docs/CLAUDE.md
- Update docs/PLATFORM-SERVICES.md deployment section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/staging.yaml

@@ -18,7 +18,7 @@ env:
   COMPOSE_FILE: docker-compose.yml
   COMPOSE_STAGING: docker-compose.staging.yml
   HEALTH_CHECK_TIMEOUT: "60"
-  LOG_LEVEL: INFO
+  LOG_LEVEL: DEBUG
 
 jobs:
   # ============================================