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/config.js

@@ -499,6 +499,21 @@ const Config = (() => {
         // Bind UI events
         bindEvents();
 
+        // Kiosk mode toggle
+        var kioskToggle = document.getElementById('cfg-kiosk-mode');
+        if (kioskToggle && window.NexusKiosk) {
+            kioskToggle.checked = window.NexusKiosk.isEnabled();
+            kioskToggle.addEventListener('change', function () {
+                if (this.checked) {
+                    window.NexusKiosk.enable();
+                    toast('Modo Kiosko activado');
+                } else {
+                    window.NexusKiosk.disable();
+                    toast('Modo Kiosko desactivado');
+                }
+            });
+        }
+
         // Load real data in parallel
         loadBranches();
         loadEmployees();