Recognize local vision models so their images aren't dropped (#185)

An image attachment only got through if the model name was on a short
built-in list. Anything else was treated as text-only and the image was
quietly dropped, so the model never saw it. That left out a lot of the
smaller vision models you can run locally (moondream was the one I hit).

Pulled the check into is_vision_model() in chat_helpers, broadened it to
cover those, and added a test. Models that already worked are unaffected.

Fixes #124.

src/chat_handler.py

@@ -15,7 +15,7 @@ from src.constants import (
     UPLOAD_DIR,
 )
 from core.models import ChatMessage
-from src.chat_helpers import extract_urls
+from src.chat_helpers import extract_urls, is_vision_model
 from src.document_processor import build_user_content, analyze_image_with_vl_result
 from src.youtube_handler import (
     is_youtube_url,
@@ -147,17 +147,7 @@ class ChatHandler:
         # Analyze images — skip if vision disabled, or if main model is vision-capable
         from src.settings import get_setting
         vision_enabled = get_setting("vision_enabled", True)
-        VISION_KEYWORDS = [
-            "gpt-4o", "gpt-4.1", "gpt-4.5", "gpt-4-turbo", "gpt-4-vision",
-            "claude-sonnet", "claude-opus", "claude-haiku",
-            "gemini", "llava", "pixtral", "qwen2-vl", "qwen-vl", "qwen3-vl", "qwen3vl", "minicpm",
-        ]
-        main_model = (sess.model or "").lower()
-        main_is_vision = any(kw in main_model for kw in VISION_KEYWORDS)
-        # Also match models with "vl" in the name (e.g. Qwen3VL, InternVL, any *-VL-*)
-        if not main_is_vision:
-            import re
-            main_is_vision = bool(re.search(r'\dvl|vl\d|[-_]vl[-_.\d]|vl-', main_model))
+        main_is_vision = is_vision_model(sess.model or "")
 
         # Read uploads DB once and index by id (was read twice + linear-scanned per attachment)
         files_by_id: Dict[str, Dict] = {}