feat: Add LangGraph streaming with real-time UI updates

- Add streaming schemas and events
- Implement run_review_stream in ReviewerAgent
- Update task_worker to broadcast streaming events via WebSocket
- Create ReviewStream component for real-time progress visualization
- Integrate ReviewStream into ReviewDetail page
- Show agent steps, LLM messages, and progress in real-time

backend/app/agents/reviewer.py

@@ -485,4 +485,56 @@ class ReviewerAgent:
         
         final_state = await self.graph.ainvoke(initial_state)
         return final_state
+    
+    async def run_review_stream(
+        self,
+        review_id: int,
+        pr_number: int,
+        repository_id: int,
+        on_event: callable = None
+    ) -> Dict[str, Any]:
+        """Run the review workflow with streaming events"""
+        initial_state: ReviewState = {
+            "review_id": review_id,
+            "pr_number": pr_number,
+            "repository_id": repository_id,
+            "status": "pending",
+            "files": [],
+            "analyzed_files": [],
+            "comments": [],
+            "error": None,
+            "git_service": None
+        }
+        
+        final_state = None
+        
+        # Stream through the graph
+        async for event in self.graph.astream(
+            initial_state,
+            stream_mode=["updates", "messages"]
+        ):
+            # Handle different event types
+            if isinstance(event, dict):
+                # Node updates
+                for node_name, node_data in event.items():
+                    if on_event:
+                        await on_event({
+                            "type": "agent_step",
+                            "step": node_name,
+                            "data": node_data
+                        })
+                    
+                    # Store final state
+                    if isinstance(node_data, dict):
+                        final_state = node_data
+            
+            # Handle message events (LLM calls)
+            elif hasattr(event, '__class__') and 'message' in event.__class__.__name__.lower():
+                if on_event:
+                    await on_event({
+                        "type": "llm_message",
+                        "message": str(event)
+                    })
+        
+        return final_state or initial_state