chore: standardize configuration, logging, and error handling across blockchain node and coordinator API

- Add infrastructure.md and workflow files to .gitignore to prevent sensitive info leaks
- Change blockchain node mempool backend default from memory to database for persistence
- Refactor blockchain node logger with StructuredLogFormatter and AuditLogger (consistent with coordinator)
- Add structured logging fields: service, module, function, line number
- Unify coordinator config with Database

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

@@ -1,10 +1,19 @@
-from typing import Callable, Annotated
+"""
+Dependency injection module for AITBC Coordinator API
+
+Provides unified dependency injection using storage.SessionDep.
+"""
+
+from typing import Callable
 from fastapi import Depends, Header, HTTPException
 
 from .config import settings
+from .storage import SessionDep
 
 
 class APIKeyValidator:
+    """Validator for API key authentication."""
+    
     def __init__(self, allowed_keys: list[str]):
         self.allowed_keys = {key.strip() for key in allowed_keys if key}
 
@@ -15,12 +24,22 @@ class APIKeyValidator:
 
 
 def require_client_key() -> Callable[[str | None], str]:
+    """Dependency for client API key authentication."""
     return APIKeyValidator(settings.client_api_keys)
 
 
 def require_miner_key() -> Callable[[str | None], str]:
+    """Dependency for miner API key authentication."""
     return APIKeyValidator(settings.miner_api_keys)
 
 
 def require_admin_key() -> Callable[[str | None], str]:
+    """Dependency for admin API key authentication."""
     return APIKeyValidator(settings.admin_api_keys)
+
+
+# Legacy aliases for backward compatibility
+def get_session():
+    """Legacy alias - use SessionDep instead."""
+    from .storage import get_session
+    return get_session()