feat: Media Explorer panel (F6) với mutual exclusion Mixer (F7)

app/templates/index.html

@@ -23,7 +23,7 @@
     <script src="/static/js/services/midiExtractor.js?v=202607281052"></script>
     <script src="/static/js/services/promptTemplateManager.js?v=202607281039"></script>
     <script src="/static/js/services/undoRedoEngine.js?v=202607290941"></script>
-    <script src="/static/js/app.precompiled.js?v=202607310809" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202607311123" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {
@@ -380,6 +380,32 @@
             border-radius: 2px;
             box-shadow: 0 4px 8px rgba(0,0,0,0.9), inset 0 1px 1px rgba(255,255,255,0.9);
         }
+
+        /* Media Explorer: horizontal volume slider + selected file row */
+        input[type=range].me-fader-slider {
+            -webkit-appearance: none;
+            appearance: none;
+            background: #111;
+            height: 6px;
+            border-radius: 3px;
+            border: 1px solid #555;
+            cursor: pointer;
+        }
+        input[type=range].me-fader-slider::-webkit-slider-thumb {
+            -webkit-appearance: none;
+            height: 16px;
+            width: 12px;
+            background: linear-gradient(180deg, #e2e8f0 0%, #64748b 50%, #1e293b 100%);
+            border: 1px solid #000;
+            border-radius: 2px;
+            box-shadow: 0 2px 4px rgba(0,0,0,0.5);
+            cursor: pointer;
+        }
+        .file-row-selected {
+            background-color: #3399ff !important;
+            color: #ffffff !important;
+        }
+        .file-row-selected .file-icon { color: #ffffff !important; }
     </style>
 </head>