feat(pos): add kiosk mode, AI vision, AI part classification, public chatbot (#19 #25 #30 #29)

- Kiosk mode: fullscreen, wake lock, auto-login, context menu block, PWA/Capacitor detection
- AI vision: camera photos analyzed by Gemma 3 27B vision model via OpenRouter
- AI part classification: auto-suggest name/brand/category when entering part number
- Public catalog chatbot: /api/chat endpoint with rate limiting, chat widget on catalog page

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/templates/login.html

@@ -1361,6 +1361,7 @@
 
   </script>
 
+  <script src="/pos/static/js/kiosk.js"></script>
   <script src="/pos/static/js/sync-engine.js"></script>
   <script>if('serviceWorker' in navigator){navigator.serviceWorker.register('/pos/sw.js',{scope:'/pos/'});}</script>