feat: chatUsageBadge-Setting + Dashboard-Menü als Dropdown

- Neues Setting chatUsageBadge (default: false) blendet Usage-Badge im Chat ein/aus
- Dashboard-Links durch 3-Dot-Header-Menü ersetzt (einheitlich mit Chat)
- Admin-Items über admin-only Attribut gesteuert, dashboard-links CSS entfernt

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

wwwroot/index.html

@@ -54,13 +54,19 @@
     <header>
       <button class="back-btn icon-btn" disabled></button>
       <h1 class="dashboard-title">// gott</h1>
-      <div class="dashboard-links">
-        <a id="dashboardSettingsLink" class="dashboard-link">Einstellungen</a>
-        <a id="dashboardAdminLink" class="dashboard-link" hidden>Benutzerverwaltung</a>
-        <a id="dashboardApiKeysLink" class="dashboard-link" hidden>API-Keys</a>
-        <a id="dashboardServerSettingsLink" class="dashboard-link" hidden>Servereinstellungen</a>
-        <a id="dashboardDbExplorerLink" class="dashboard-link" hidden>Datenbank</a>
-        <a id="dashboardProfileLink" class="dashboard-link">Mein Profil</a>
+      <div class="header-menu">
+        <button class="header-menu-trigger icon-btn" id="dashboardMenuBtn"><i class="fa fa-ellipsis-v"></i></button>
+        <div class="header-menu-dropdown" id="dashboardMenuDropdown" hidden>
+          <div class="header-menu-label">Benutzer</div>
+          <button class="header-menu-item" id="dashboardProfileLink"><i class="fa fa-user"></i> Mein Profil</button>
+          <button class="header-menu-item" id="dashboardSettingsLink"><i class="fa fa-cog"></i> Einstellungen</button>
+          <div class="header-menu-separator" hidden admin-only></div>
+          <div class="header-menu-label" hidden admin-only>Administrator</div>
+          <button class="header-menu-item" id="dashboardServerSettingsLink" hidden admin-only><i class="fa fa-server"></i> Servereinstellungen</button>
+          <button class="header-menu-item" id="dashboardAdminLink" hidden admin-only><i class="fa fa-users"></i> Benutzerverwaltung</button>
+          <button class="header-menu-item" id="dashboardDbExplorerLink" hidden admin-only><i class="fa fa-database"></i> Datenbank</button>
+          <button class="header-menu-item" id="dashboardApiKeysLink" hidden admin-only><i class="fa fa-key"></i> API-Keys</button>
+        </div>
       </div>
     </header>
     <div class="page-content">
@@ -473,6 +479,18 @@
               </label>
             </div>
           </div>
+          <div class="setting-row">
+            <div class="setting-info">
+              <label>Usage-Badge</label>
+              <span class="setting-hint">API-Key-Verbrauch im Chat anzeigen</span>
+            </div>
+            <div class="setting-control">
+              <label class="toggle-switch">
+                <input type="checkbox" id="settingChatUsageBadge">
+                <span class="toggle-slider"></span>
+              </label>
+            </div>
+          </div>
         </section>
         <section id="settingsBackupSection" class="settings-section" hidden>
           <h2>Daten</h2>