Add configurable library path with settings API and UI

public/app.js

@@ -5,6 +5,7 @@ const API_BASE = window.location.origin;
 document.addEventListener('DOMContentLoaded', () => {
     loadDashboard();
     updateSubsonicUrl();
+    loadSettings();
 });
 
 // Switch between tabs
@@ -296,3 +297,48 @@ function updateSubsonicUrl() {
     const url = `${window.location.protocol}//${window.location.hostname}:${window.location.port}/rest`;
     document.getElementById('subsonicUrl').value = url;
 }
+
+// Load settings
+async function loadSettings() {
+    try {
+        const res = await fetch(`${API_BASE}/api/settings`);
+        const settings = await res.json();
+        document.getElementById('libraryPath').value = settings.libraryPath;
+    } catch (error) {
+        console.error('Error loading settings:', error);
+    }
+}
+
+// Save library path
+async function saveLibraryPath() {
+    const libraryPath = document.getElementById('libraryPath').value;
+    
+    if (!libraryPath) {
+        alert('Please enter a library path');
+        return;
+    }
+    
+    try {
+        const res = await fetch(`${API_BASE}/api/settings`, {
+            method: 'PATCH',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ libraryPath })
+        });
+        
+        const data = await res.json();
+        
+        if (res.ok) {
+            alert('Library path updated! Please restart the server for changes to take effect.');
+        } else {
+            alert(`Error: ${data.error}`);
+        }
+    } catch (error) {
+        console.error('Error saving settings:', error);
+        alert('Failed to save settings');
+    }
+}
+
+// Browse for folder (note: web browsers can't actually browse filesystem)
+function browseFolder() {
+    alert('Enter the full path to your audio library folder.\n\nExamples:\n- /Users/username/Music\n- /home/user/music\n- C:\\Users\\username\\Music\n- ./audio_library (relative to server)');
+}