Refa: refine retry gap. (#8773)

### What problem does this PR solve?

### Type of change

- [x] Refactoring
- [x] Performance Improvement

rag/llm/chat_model.py

 
     def _get_delay(self):
         """Calculate retry delay time"""
-        return self.base_delay + random.uniform(0, 0.5)
+        return self.base_delay + random.uniform(10, 150)
 
     def _classify_error(self, error):
         """Classify error based on error message content"""