🔒 Add privacy settings for leaderboard visibility

✨ Features:
- Added show_in_leaderboard column to players table (default: false)
- Replaced Quick Actions with Settings section in dashboard
- Added toggle switch for leaderboard visibility
- Created settings modal with privacy controls

🔧 API Changes:
- Added /api/v1/private/update-player-settings endpoint
- Updated best-times queries to filter by show_in_leaderboard
- Updated times-with-details to respect privacy settings
- Added updated_at column to players table

🎨 UI/UX:
- Modern toggle switch design
- Responsive settings modal
- Success/error notifications
- Clear privacy explanation

🔐 Privacy:
- Default: Times are NOT shown in global leaderboard
- Users can opt-in via settings
- Personal dashboard always shows own times
- Global leaderboard only shows opted-in users

public/css/dashboard.css

@@ -1380,3 +1380,119 @@ body {
     color: #b3e5fc;
     font-size: 0.85rem;
 }
+
+/* Settings Modal Styles */
+.settings-content {
+    padding: 1.5rem 0;
+}
+
+.setting-item {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 1.5rem;
+    background: #1e293b;
+    border-radius: 0.75rem;
+    margin-bottom: 1rem;
+    border: 1px solid #334155;
+}
+
+.setting-info h3 {
+    color: #ffffff;
+    font-size: 1.1rem;
+    font-weight: 600;
+    margin-bottom: 0.5rem;
+}
+
+.setting-info p {
+    color: #8892b0;
+    font-size: 0.9rem;
+    line-height: 1.4;
+}
+
+.setting-control {
+    margin-left: 1rem;
+}
+
+/* Toggle Switch Styles */
+.toggle-switch {
+    position: relative;
+    display: inline-block;
+    width: 60px;
+    height: 34px;
+}
+
+.toggle-switch input {
+    opacity: 0;
+    width: 0;
+    height: 0;
+}
+
+.toggle-slider {
+    position: absolute;
+    cursor: pointer;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    background-color: #334155;
+    transition: 0.3s;
+    border-radius: 34px;
+}
+
+.toggle-slider:before {
+    position: absolute;
+    content: "";
+    height: 26px;
+    width: 26px;
+    left: 4px;
+    bottom: 4px;
+    background-color: white;
+    transition: 0.3s;
+    border-radius: 50%;
+}
+
+input:checked + .toggle-slider {
+    background-color: #00d4ff;
+}
+
+input:checked + .toggle-slider:before {
+    transform: translateX(26px);
+}
+
+.setting-description {
+    margin-top: 1rem;
+}
+
+.settings-actions {
+    display: flex;
+    gap: 1rem;
+    margin-top: 2rem;
+    justify-content: flex-end;
+}
+
+.settings-actions .btn {
+    min-width: 120px;
+}
+
+/* Responsive Settings */
+@media (max-width: 768px) {
+    .setting-item {
+        flex-direction: column;
+        align-items: flex-start;
+        gap: 1rem;
+    }
+    
+    .setting-control {
+        margin-left: 0;
+        align-self: flex-end;
+    }
+    
+    .settings-actions {
+        flex-direction: column;
+    }
+    
+    .settings-actions .btn {
+        width: 100%;
+    }
+}