fix circular deps issue

app/core/dependencies.py

@@ -0,0 +1,17 @@
+"""Dependency injection for services."""
+
+from typing import Optional
+from app.services.base import InferenceService
+
+_inference_service: Optional[InferenceService] = None
+
+
+def get_inference_service() -> Optional[InferenceService]:
+    """Get inference service for dependency injection."""
+    return _inference_service
+
+
+def set_inference_service(service: InferenceService) -> None:
+    """Set inference service. Called internally during startup."""
+    global _inference_service
+    _inference_service = service