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/static/js/chat.js

@@ -200,8 +200,9 @@
       container.insertBefore(div, typing);
       scrollToBottom();
 
-      // Send to AI as a text description (vision model placeholder)
-      const photoPrompt = 'El usuario envio una foto de una parte automotriz. Describe que parte podria ser y sugiere busquedas.';
+      // Send image to AI vision model for real analysis
+      var imageData = ev.target.result;  // full data URL
+      var photoPrompt = 'Identifica esta parte automotriz y sugiere terminos de busqueda.';
       history.push({ role: 'user', content: photoPrompt });
       if (history.length > 20) history.splice(0, 2);
 
@@ -209,7 +210,7 @@
       document.getElementById('chatSend').disabled = true;
       showTyping(true);
 
-      const token = getToken();
+      var token = getToken();
       fetch('/pos/api/chat', {
         method: 'POST',
         headers: {
@@ -218,6 +219,7 @@
         },
         body: JSON.stringify({
           message: photoPrompt,
+          image: imageData,
           history: history.slice(-10)
         })
       })