Settings: left sidebar nav with separate page views per category

Replaced horizontal tab bar with a left sidebar navigation
that feels like separate pages:
- Left nav with icons + labels (Connection, Audio, 4CM Routing,
  Network, Bluetooth, About)
- Active category highlighted in accent color
- Each category has its own URL via hash (#connection, #audio, etc.)
- Back/forward browser navigation via popstate handler
- Stacked layout on mobile (sidebar becomes scrollable row)

src/web/static/style.css

@@ -696,43 +696,87 @@ body {
     line-height: 1.4;
 }
 
-/* ── Settings tabs ────────────────────────────────────────────────── */
+/* ── Settings layout: sidebar + content ──────────────────────────── */
 
-.settings-tabs {
+.settings-layout {
     display: flex;
-    gap: 4px;
-    overflow-x: auto;
-    -webkit-overflow-scrolling: touch;
-    scrollbar-width: none;
-    margin-bottom: 12px;
-    padding-bottom: 4px;
-    border-bottom: 1px solid var(--border);
+    gap: 16px;
+    align-items: flex-start;
 }
 
-.settings-tabs::-webkit-scrollbar {
-    display: none;
+/* ── Settings sidebar ──────────────────────────────────────────────── */
+
+.settings-sidebar {
+    width: 180px;
+    flex-shrink: 0;
+    display: flex;
+    flex-direction: column;
+    gap: 2px;
+    background: var(--bg-secondary);
+    border: 1px solid var(--border);
+    border-radius: var(--radius);
+    padding: 6px;
+    position: sticky;
+    top: 12px;
 }
 
-.settings-tab {
-    padding: 8px 14px;
+.settings-nav-item {
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    padding: 10px 12px;
+    border-radius: 6px;
+    text-decoration: none;
+    color: var(--text-secondary);
+    font-size: 0.85rem;
+    font-weight: 500;
+    transition: all 0.15s;
+    cursor: pointer;
+    touch-action: manipulation;
     border: none;
     background: transparent;
-    color: var(--text-secondary);
-    font-size: 0.82rem;
-    cursor: pointer;
-    white-space: nowrap;
-    border-bottom: 2px solid transparent;
-    transition: color 0.2s, border-color 0.2s;
-    touch-action: manipulation;
+    width: 100%;
+    text-align: left;
 }
 
-.settings-tab:hover {
+.settings-nav-item:hover {
+    background: var(--bg-hover);
     color: var(--text-primary);
 }
 
-.settings-tab.active {
-    color: var(--accent);
-    border-bottom-color: var(--accent);
+.settings-nav-item.active {
+    background: var(--accent);
+    color: #000;
+    font-weight: 600;
+}
+
+.settings-nav-item.active .settings-nav-icon {
+    filter: none;
+}
+
+.settings-nav-icon {
+    font-size: 1rem;
+    width: 22px;
+    text-align: center;
+    flex-shrink: 0;
+    opacity: 0.7;
+}
+
+.settings-nav-item.active .settings-nav-icon {
+    opacity: 1;
+}
+
+.settings-nav-label {
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+/* ── Settings content panel ──────────────────────────────────────────── */
+
+.settings-content {
+    flex: 1;
+    min-width: 0;
 }
 
 .settings-panel {
@@ -743,6 +787,33 @@ body {
     display: block;
 }
 
+/* Mobile: stack sidebar above content */
+@media (max-width: 640px) {
+    .settings-layout {
+        flex-direction: column;
+    }
+    .settings-sidebar {
+        width: 100%;
+        flex-direction: row;
+        overflow-x: auto;
+        position: static;
+        scrollbar-width: none;
+    }
+    .settings-sidebar::-webkit-scrollbar {
+        display: none;
+    }
+    .settings-nav-item {
+        white-space: nowrap;
+        flex-shrink: 0;
+        padding: 8px 12px;
+        font-size: 0.8rem;
+    }
+    .settings-nav-icon {
+        font-size: 0.85rem;
+        width: 18px;
+    }
+}
+
 /* ── Network UI ──────────────────────────────────────────────────── */
 
 .network-status-row {

src/web/templates/settings.html

@@ -6,16 +6,37 @@
         <h1>Settings</h1>
     </div>
 
-    <!-- Tab navigation -->
-    <div class="settings-tabs">
-        <button class="settings-tab active" data-tab="connection" onclick="switchTab('connection')">Connection</button>
-        <button class="settings-tab" data-tab="audio" onclick="switchTab('audio')">Audio</button>
-        <button class="settings-tab" data-tab="routing" onclick="switchTab('routing')">4CM Routing</button>
-        <button class="settings-tab" data-tab="network" onclick="switchTab('network')">Network</button>
-        <button class="settings-tab" data-tab="bluetooth" onclick="switchTab('bluetooth')">Bluetooth</button>
-        <button class="settings-tab" data-tab="about" onclick="switchTab('about')">About</button>
-    </div>
+    <div class="settings-layout">
+        <!-- Left sidebar navigation -->
+        <nav class="settings-sidebar">
+            <a class="settings-nav-item active" href="#connection" data-tab="connection" onclick="switchTab('connection')">
+                <span class="settings-nav-icon">🔌</span>
+                <span class="settings-nav-label">Connection</span>
+            </a>
+            <a class="settings-nav-item" href="#audio" data-tab="audio" onclick="switchTab('audio')">
+                <span class="settings-nav-icon">🎚️</span>
+                <span class="settings-nav-label">Audio</span>
+            </a>
+            <a class="settings-nav-item" href="#routing" data-tab="routing" onclick="switchTab('routing')">
+                <span class="settings-nav-icon">🔀</span>
+                <span class="settings-nav-label">4CM Routing</span>
+            </a>
+            <a class="settings-nav-item" href="#network" data-tab="network" onclick="switchTab('network')">
+                <span class="settings-nav-icon">📶</span>
+                <span class="settings-nav-label">Network</span>
+            </a>
+            <a class="settings-nav-item" href="#bluetooth" data-tab="bluetooth" onclick="switchTab('bluetooth')">
+                <span class="settings-nav-icon">🔵</span>
+                <span class="settings-nav-label">Bluetooth</span>
+            </a>
+            <a class="settings-nav-item" href="#about" data-tab="about" onclick="switchTab('about')">
+                <span class="settings-nav-icon">ℹ️</span>
+                <span class="settings-nav-label">About</span>
+            </a>
+        </nav>
 
+        <!-- Content area -->
+        <div class="settings-content">
             <!-- Tab: Connection -->
             <div class="settings-panel active" id="tab-connection">
                 <div class="card">
@@ -60,6 +81,22 @@
                                 </button>
                             </div>
                         </div>
+                        <div class="setting-row" style="border-bottom:none">
+                            <div class="setting-label">Latency Profile</div>
+                            <div class="setting-value">
+                                <select id="audio-profile-select" class="profile-select"
+                                        onchange="switchAudioProfile(this.value)">
+                                    <option value="">Loading...</option>
+                                </select>
+                            </div>
+                        </div>
+                        <div class="setting-row" style="border-bottom:none">
+                            <div class="setting-label">JACK Status</div>
+                            <div class="setting-value">
+                                <span id="jack-status" class="jack-check">—</span>
+                                <button class="btn btn-secondary btn-sm" onclick="refreshAudioProfile()">⟳</button>
+                            </div>
+                        </div>
                     </div>
                 </div>
             </div>
@@ -263,6 +300,8 @@
                     </div>
                 </div>
             </div>
+        </div>
+    </div>
 
     <!-- WiFi connect modal -->
     <div class="modal-overlay" id="wifi-connect-modal" style="display:none;" onclick="if(event.target===this)closeWiFiModal()">
@@ -293,13 +332,21 @@
 <script src="/static/network.js"></script>
 <script src="/static/bluetooth.js"></script>
 <script>
-/* ── Tab switching ────────────────────────────────────────────────── */
+/* ── Tab switching (left nav) ──────────────────────────────────── */
 function switchTab(tabId) {
-    document.querySelectorAll('.settings-tab').forEach(t => t.classList.remove('active'));
+    // Update nav items
+    document.querySelectorAll('.settings-nav-item').forEach(a => a.classList.remove('active'));
+    document.querySelector(`.settings-nav-item[data-tab="${tabId}"]`).classList.add('active');
+
+    // Update panels
     document.querySelectorAll('.settings-panel').forEach(p => p.classList.remove('active'));
-    document.querySelector(`.settings-tab[data-tab="${tabId}"]`).classList.add('active');
     document.getElementById(`tab-${tabId}`).classList.add('active');
 
+    // Sync URL hash
+    if (window.location.hash !== `#${tabId}`) {
+        history.pushState(null, '', `#${tabId}`);
+    }
+
     // Refresh tab data when switching to it
     if (tabId === 'network') {
         refreshWiFiStatus();
@@ -308,14 +355,25 @@ function switchTab(tabId) {
         refreshBTStatus();
         refreshBTMIDIStatus();
         loadPairedDevices();
+    } else if (tabId === 'audio') {
+        refreshAudioProfile();
     }
 }
 
-/* ── Initial load on settings page ───────────────────────────────── */
+/* ── Initial load & hash routing ───────────────────────────────── */
 document.addEventListener('DOMContentLoaded', () => {
-    // Check if we should auto-switch based on URL hash
     const hash = window.location.hash.replace('#', '');
-    if (['network', 'bluetooth', 'audio', 'routing', 'about'].includes(hash)) {
+    const valid = ['connection', 'audio', 'routing', 'network', 'bluetooth', 'about'];
+    if (valid.includes(hash)) {
+        switchTab(hash);
+    }
+});
+
+/* ── Listen for back/forward navigation ───────────────────────── */
+window.addEventListener('popstate', () => {
+    const hash = window.location.hash.replace('#', '');
+    const valid = ['connection', 'audio', 'routing', 'network', 'bluetooth', 'about'];
+    if (valid.includes(hash)) {
         switchTab(hash);
     }
 });