fix: Check chat_template is set before using apply_chat_template

The tokenizer has the apply_chat_template method but no template
configured. Now we check tokenizer.chat_template is not None
before attempting to use it, falling back to manual [INST] format.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/model_service.py

@@ -1467,7 +1467,12 @@ async def analyze_research_attention(request: Dict[str, Any], authenticated: boo
 
         # Format prompt for chat/instruct models
         if uses_chat_template:
-            if hasattr(manager.tokenizer, 'apply_chat_template'):
+            # Check if tokenizer has a chat template actually configured (not just the method)
+            has_template = (
+                hasattr(manager.tokenizer, 'chat_template') and
+                manager.tokenizer.chat_template is not None
+            )
+            if has_template:
                 # Use tokenizer's built-in chat template
                 messages = [{"role": "user", "content": f"Complete the following code:\n{prompt}"}]
                 formatted_prompt = manager.tokenizer.apply_chat_template(