Add configurable library path with settings API and UI

public/index.html

@@ -358,10 +358,16 @@
                 <h2>Library Settings</h2>
                 <div class="form-group">
                     <label>Library Path</label>
-                    <input type="text" id="libraryPath" value="./audio_library" readonly>
-                    <small style="color: #86868b;">Audio files location on server</small>
+                    <div style="display: flex; gap: 10px;">
+                        <input type="text" id="libraryPath" placeholder="/path/to/your/music" style="flex: 1; margin-bottom: 0;">
+                        <button class="btn btn-secondary" onclick="browseFolder()" style="white-space: nowrap;">💡 Help</button>
+                    </div>
+                    <small style="color: #86868b;">Full path or relative path to your audio files</small>
+                </div>
+                <div style="display: flex; gap: 10px;">
+                    <button class="btn btn-primary" onclick="saveLibraryPath()">Save Path</button>
+                    <button class="btn btn-secondary" onclick="scanLibrary()">Scan Library</button>
                 </div>
-                <button class="btn btn-primary" onclick="scanLibrary()">Scan Library Now</button>
             </div>
 
             <div class="card">