fix: Improve Docker container shutdown handling

- Add proper signal handlers for graceful shutdown of all components
- Implement WebhookBatcher.shutdown() to properly close ThreadPoolExecutor and cancel timers
- Add NFOGuardDatabase.close() method to close thread-local database connections
- Increase uvicorn graceful shutdown timeout to 15 seconds
- Add cleanup in finally block to ensure resources are freed even if signal handler fails
- Reduce logging and server header overhead for better performance

This should resolve Docker container shutdown issues where containers don't respond to SIGTERM properly.

Bump version to 2.1.1

🤖 Generated with [Claude Code](https://claude.ai/code)

webhooks/webhook_batcher.py

@@ -172,4 +172,33 @@ class WebhookBatcher:
                 "processing_items": list(self.processing),
                 "pending_count": len(self.pending),
                 "processing_count": len(self.processing)
-            }
+            }
+    
+    def shutdown(self):
+        """Shutdown the webhook batcher gracefully"""
+        _log("INFO", "Shutting down webhook batcher...")
+        
+        with self.lock:
+            # Cancel all pending timers
+            for timer in self.timers.values():
+                try:
+                    timer.cancel()
+                except Exception as e:
+                    _log("WARNING", f"Error canceling timer: {e}")
+            
+            self.timers.clear()
+            
+            # Log any remaining items
+            if self.pending:
+                _log("WARNING", f"Shutting down with {len(self.pending)} pending items")
+            if self.processing:
+                _log("INFO", f"Waiting for {len(self.processing)} items to finish processing...")
+        
+        # Shutdown the thread pool executor
+        try:
+            self.executor.shutdown(wait=True, timeout=10)  # Wait up to 10 seconds
+            _log("INFO", "Thread pool executor shut down successfully")
+        except Exception as e:
+            _log("WARNING", f"Error shutting down thread pool: {e}")
+        
+        _log("INFO", "Webhook batcher shutdown complete")