Changed content manager group behavior and added save button

public/index.html

@@ -305,7 +305,8 @@
                 </label>
                 <div class="setting-info">
                   <span class="setting-label">Force Backend Proxy</span>
-                  <span class="setting-hint">Route all streams through the proxy server. Enable if streams don't play directly.</span>
+                  <span class="setting-hint">Route all streams through the proxy server. Enable if streams don't play
+                    directly.</span>
                 </div>
               </div>
             </div>
@@ -339,6 +340,7 @@
                 <div class="content-actions">
                   <button class="btn btn-sm btn-secondary" id="content-show-all">Show All</button>
                   <button class="btn btn-sm btn-secondary" id="content-hide-all">Hide All</button>
+                  <button class="btn btn-sm btn-primary" id="content-save">💾 Save Changes</button>
                 </div>
               </div>
               <p class="hint" style="margin-bottom: var(--space-sm);">✓ Checked = Visible, ☐ Unchecked = Hidden</p>