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/schemas/__init__.py

@@ -16,6 +16,13 @@ from app.schemas.webhook import (
     GitHubWebhook,
     BitbucketWebhook
 )
+from app.schemas.streaming import (
+    StreamEvent,
+    AgentStepEvent,
+    LLMStreamEvent,
+    ReviewProgressEvent,
+    StreamEventType
+)
 
 __all__ = [
     "RepositoryCreate",
@@ -28,5 +35,10 @@ __all__ = [
     "GiteaWebhook",
     "GitHubWebhook",
     "BitbucketWebhook",
+    "StreamEvent",
+    "AgentStepEvent",
+    "LLMStreamEvent",
+    "ReviewProgressEvent",
+    "StreamEventType",
 ]