style(header): remove logo subtitle and center instance title next to icon

frontend/src/App.tsx

@@ -484,14 +484,9 @@ export const App: React.FC = () => {
             <div className="w-7 h-7 bg-accent text-on-accent rounded-btn flex items-center justify-center">
               <Brain className="w-4 h-4" />
             </div>
-            <div className="flex flex-col">
-              <span className="font-bold text-sm sm:text-base text-main tracking-tight leading-none">
-                {authStatus.instanceName || 'MindSift'}
-              </span>
-              <span className="text-[11px] text-muted mt-0.5 hidden sm:inline-block">
-                Der Kopf frei in drei Sekunden
-              </span>
-            </div>
+            <span className="font-bold text-sm sm:text-base text-main tracking-tight leading-none">
+              {authStatus.instanceName || 'MindSift'}
+            </span>
           </div>
 
           {/* Quick-Capture Input Bubble directly in Header (above Tabs) */}