feat(voice): implementa voz y TTS en chats POS y dashboard

- Agrega TTS (speechSynthesis) a chat.js del POS para leer respuestas IA
- Copia lógica de voz completa (STT + TTS) a dashboard/chat-public.js
- Extiende estilos TTS en chat.css y chat-public.css
- Agrega chat widget a 13 templates POS que no lo tenían
- Corrige duplicado de chat.css en diagrams.html
- Minifica assets actualizados
- 73/73 tests pasan

dashboard/chat-public.js

@@ -1,15 +1,20 @@
 // /home/Autopartes/dashboard/chat-public.js
-// Public catalog chatbot — no auth required, calls /api/chat
+// Public catalog chatbot — voice + TTS enabled
 
 (function () {
   'use strict';
 
   var isOpen = false;
   var isSending = false;
+  var isListening = false;
+  var recognition = null;
   var history = [];
+  var ttsEnabled = true;
+  var ttsUtterance = null;
+  var hasSpeechAPI = ('webkitSpeechRecognition' in window || 'SpeechRecognition' in window);
+  var hasTTS = ('speechSynthesis' in window);
 
   function init() {
-    // FAB button
     var fab = document.createElement('button');
     fab.className = 'chat-fab';
     fab.id = 'chatFab';
@@ -17,14 +22,16 @@
     fab.innerHTML = '💬';
     fab.setAttribute('aria-label', 'Abrir asistente IA');
 
-    // Chat panel
     var panel = document.createElement('div');
     panel.className = 'chat-panel';
     panel.id = 'chatPanel';
     panel.innerHTML =
       '<div class="chat-header">' +
         '<h3>Asistente — Buscar partes</h3>' +
-        '<button class="chat-header-close" id="chatClose" aria-label="Cerrar">&times;</button>' +
+        '<div class="chat-header-actions">' +
+          (hasTTS ? '<button class="chat-tts-toggle" id="chatTtsToggle" aria-label="Activar lectura de respuestas" title="Activar lectura de respuestas">&#128266;</button>' : '') +
+          '<button class="chat-header-close" id="chatClose" aria-label="Cerrar">&times;</button>' +
+        '</div>' +
       '</div>' +
       '<div class="chat-messages" id="chatMessages">' +
         '<div class="chat-msg ai">Hola, soy el asistente de Nexus Autoparts. Dime que refaccion buscas y te ayudo a encontrarla en el catalogo.</div>' +
@@ -32,6 +39,7 @@
       '</div>' +
       '<div class="chat-input-area">' +
         '<textarea class="chat-input" id="chatInput" placeholder="Ej: Balatas para Tsuru 2015..." rows="1"></textarea>' +
+        (hasSpeechAPI ? '<button class="chat-mic-btn" id="chatMic" aria-label="Entrada por voz" title="Entrada por voz">&#127908;</button>' : '') +
         '<button class="chat-send-btn" id="chatSend" aria-label="Enviar">&#9654;</button>' +
       '</div>';
 
@@ -52,8 +60,139 @@
       this.style.height = 'auto';
       this.style.height = Math.min(this.scrollHeight, 80) + 'px';
     });
+
+    if (hasSpeechAPI) {
+      document.getElementById('chatMic').addEventListener('click', toggleVoice);
+    }
+
+    if (hasTTS) {
+      document.getElementById('chatTtsToggle').addEventListener('click', toggleTTS);
+    }
+
+    // Stop TTS when closing chat
+    document.getElementById('chatClose').addEventListener('click', function () {
+      if (hasTTS) stopSpeaking();
+    });
   }
 
+  // ─── TTS ───
+  function toggleTTS() {
+    ttsEnabled = !ttsEnabled;
+    var btn = document.getElementById('chatTtsToggle');
+    if (btn) {
+      btn.classList.toggle('off', !ttsEnabled);
+      btn.setAttribute('title', ttsEnabled ? 'Desactivar lectura de respuestas' : 'Activar lectura de respuestas');
+    }
+    if (!ttsEnabled) stopSpeaking();
+  }
+
+  function speak(text) {
+    if (!hasTTS || !ttsEnabled || !text) return;
+    stopSpeaking();
+    ttsUtterance = new SpeechSynthesisUtterance(text);
+    ttsUtterance.lang = 'es-MX';
+    ttsUtterance.rate = 1.1;
+    ttsUtterance.pitch = 1;
+    window.speechSynthesis.speak(ttsUtterance);
+  }
+
+  function stopSpeaking() {
+    if (hasTTS && window.speechSynthesis.speaking) {
+      window.speechSynthesis.cancel();
+    }
+    ttsUtterance = null;
+  }
+
+  // ─── Voice Input ───
+  function toggleVoice() {
+    if (isListening) { stopVoice(); return; }
+    startVoice();
+  }
+
+  function startVoice() {
+    var SpeechRecognition = window.SpeechRecognition || window.webkitSpeechRecognition;
+    if (!SpeechRecognition) return;
+
+    recognition = new SpeechRecognition();
+    recognition.lang = 'es-MX';
+    recognition.continuous = false;
+    recognition.interimResults = true;
+
+    var input = document.getElementById('chatInput');
+    var micBtn = document.getElementById('chatMic');
+    var savedPlaceholder = input.placeholder;
+
+    recognition.onstart = function () {
+      isListening = true;
+      micBtn.classList.add('listening');
+      input.placeholder = 'Escuchando...';
+      input.value = '';
+      stopSpeaking();
+    };
+
+    recognition.onresult = function (e) {
+      var interim = '';
+      var finalTranscript = '';
+      for (var i = e.resultIndex; i < e.results.length; i++) {
+        if (e.results[i].isFinal) {
+          finalTranscript += e.results[i][0].transcript;
+        } else {
+          interim += e.results[i][0].transcript;
+        }
+      }
+      if (finalTranscript) {
+        input.value = finalTranscript;
+      } else {
+        input.value = interim;
+      }
+    };
+
+    recognition.onend = function () {
+      isListening = false;
+      micBtn.classList.remove('listening');
+      input.placeholder = savedPlaceholder;
+      recognition = null;
+      if (input.value.trim()) {
+        sendMessage();
+      }
+    };
+
+    recognition.onerror = function (e) {
+      isListening = false;
+      micBtn.classList.remove('listening');
+      input.placeholder = savedPlaceholder;
+      recognition = null;
+      if (e.error === 'no-speech' || e.error === 'audio-capture' || e.error === 'not-allowed') {
+        showVoiceToast('No se detecto voz');
+      }
+    };
+
+    recognition.start();
+  }
+
+  function stopVoice() {
+    if (recognition) {
+      recognition.abort();
+      recognition = null;
+    }
+    isListening = false;
+    var micBtn = document.getElementById('chatMic');
+    if (micBtn) micBtn.classList.remove('listening');
+  }
+
+  function showVoiceToast(msg) {
+    var toast = document.createElement('div');
+    toast.className = 'chat-voice-toast';
+    toast.textContent = msg;
+    document.body.appendChild(toast);
+    setTimeout(function () { toast.classList.add('visible'); }, 10);
+    setTimeout(function () {
+      toast.classList.remove('visible');
+      setTimeout(function () { toast.remove(); }, 300);
+    }, 2000);
+  }
+
+  // ─── Chat UI ───
   function toggleChat() {
     isOpen = !isOpen;
     var panel = document.getElementById('chatPanel');
@@ -104,6 +243,8 @@
         addBubble(aiMsg, 'ai');
         history.push({ role: 'assistant', content: aiMsg });
 
+        if (ttsEnabled) speak(aiMsg);
+
         if (data.search_results && data.search_results.length > 0) {
           addPartResults(data.search_results);
         }
@@ -149,7 +290,6 @@
 
       card.style.cursor = 'pointer';
       card.addEventListener('click', function () {
-        // Search in catalog
         var searchInput = document.getElementById('searchInput');
         if (searchInput && partNum) {
           searchInput.value = partNum;