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/config.html

@@ -1699,6 +1699,16 @@
                 <span class="toggle__slider"></span>
               </label>
             </div>
+            <div class="toggle-row">
+              <div class="toggle-row__info">
+                <span class="toggle-row__label">Modo Kiosko</span>
+                <span class="toggle-row__desc">Pantalla completa, bloqueo de pantalla activa, sin menú contextual (ideal para tablet/mostrador)</span>
+              </div>
+              <label class="toggle">
+                <input type="checkbox" id="cfg-kiosk-mode" />
+                <span class="toggle__slider"></span>
+              </label>
+            </div>
           </div>
         </div>
 
@@ -1917,6 +1927,7 @@
   <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
+  <script src="/pos/static/js/kiosk.js"></script>
   <script src="/pos/static/js/config.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>