```

chore: refactor logging module, update genesis timestamp, remove model relationships, and reorganize routers

- Rename logging.py to logger.py and update import paths in poa.py and main.py
- Update devnet genesis timestamp to 1766828620
- Remove SQLModel Relationship declarations from Block, Transaction, and Receipt models
- Add SessionDep type alias and get_session dependency in coordinator-api deps
- Reorganize coordinator-api routers: replace explorer/registry with exchange, users, marketplace

apps/coordinator-api/src/app/logging.py

@@ -0,0 +1,25 @@
+"""
+Logging configuration for the AITBC Coordinator API
+"""
+
+import logging
+import sys
+from typing import Any, Dict
+
+
+def setup_logging(level: str = "INFO") -> None:
+    """Setup structured logging for the application."""
+    logging.basicConfig(
+        level=getattr(logging, level.upper()),
+        format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
+        handlers=[logging.StreamHandler(sys.stdout)]
+    )
+
+
+def get_logger(name: str) -> logging.Logger:
+    """Get a logger instance."""
+    return logging.getLogger(name)
+
+
+# Initialize default logging on import
+setup_logging()