Limit vision model to 2 most recent images to prevent slow/hanging requests

Multiple large base64 images can overwhelm the vision model. Now we:
1. First pass: identify the 2 most recent image messages
2. Second pass: build chat history, skipping older images

app.py

@@ -1881,11 +1881,32 @@ def chat_gpt(username, room_name, model_name="gpt-4o-mini"):
         )
 
         chat_history = []
+        max_images = 2  # Limit images to prevent slow/hanging requests
+
+        # First pass: identify image messages to include (most recent N)
+        # last_messages is newest-first, so iterate in that order to find recent images
+        image_msg_ids_to_include = set()
+        if vision_enabled:
+            for msg in last_messages:  # newest first
+                is_image_msg = msg.is_base64_image() or extract_external_image_url(msg.content)
+                if is_image_msg:
+                    if len(image_msg_ids_to_include) < max_images:
+                        image_msg_ids_to_include.add(msg.id)
+                    # Continue to count all images for logging
+            if len(image_msg_ids_to_include) > 0:
+                print(f"Vision: including {len(image_msg_ids_to_include)} most recent images")
+
+        # Second pass: build chat history (oldest first)
         for msg in reversed(last_messages):
             # Skip images for non-vision models
             if msg.is_base64_image() and not vision_enabled:
                 continue
 
+            # For vision models, skip old images not in our include set
+            is_image_msg = msg.is_base64_image() or extract_external_image_url(msg.content)
+            if vision_enabled and is_image_msg and msg.id not in image_msg_ids_to_include:
+                continue
+
             role = "assistant" if msg.username in SYSTEM_USERS else "user"
             content = build_message_content(msg, vision_enabled, room_id=room_id)
             chat_history.append({"role": role, "content": content})