feat(chat): Implement real-time SSE streaming with reasoning steps and improved UI indicators.

backend/src/ea_chatbot/api/utils.py

@@ -52,6 +52,11 @@ def decode_access_token(token: str) -> Optional[dict]:
 
 def convert_to_json_compatible(obj: Any) -> Any:
     """Recursively convert LangChain objects, Pydantic models, and others to JSON compatible formats."""
+    # Handle known non-serializable types first to avoid recursion
+    type_name = type(obj).__name__
+    if type_name == "Figure" or type_name == "DataFrame":
+        return f"<{type_name} object>"
+
     if isinstance(obj, list):
         return [convert_to_json_compatible(item) for item in obj]
     elif isinstance(obj, dict):
@@ -91,4 +96,11 @@ def convert_to_json_compatible(obj: Any) -> Any:
         return str(obj.content)
     elif isinstance(obj, (datetime, timezone)):
         return obj.isoformat()
-    return obj
+    
+    # Final fallback for any other types that might not be JSON serializable
+    import json
+    try:
+        json.dumps(obj)
+        return obj
+    except (TypeError, OverflowError):
+        return str(obj)