Logo im Dark Mode sichtbar, Apps öffnen in neuem Tab

- Logo mit fest weißen Palmen statt transparenter Aussparung (war auf dunklem Grund unsichtbar)
- App-Kacheln (Portal und Kopfleiste) öffnen standardmäßig einen neuen Tab (OPEN_APPS_IN_NEW_TAB)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

frontend/index.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="theme-color" content="#2d1b69" />
     <script src="/theme-init.js"></script>
-    <link rel="icon" type="image/png" href="/favicon.png" />
+    <link rel="icon" type="image/png" href="/favicon.png?v=2" />
     <link rel="apple-touch-icon" href="/icon-192.png" />
     <title>Handy-Insel Portal</title>
   </head>

frontend/src/App.tsx

@@ -70,7 +70,7 @@ function Header({ user, links }: { user: User; links: Links }) {
     <header className="sticky top-0 z-20 border-b border-line bg-surface">
       <div className="flex h-14 items-center justify-between px-4 sm:px-6">
         <a href="/" className="flex items-center gap-2.5" aria-label="Handy-Insel Portal">
-          <img src="/icon-192.png" alt="" className="logo-badge h-8 w-8 rounded-full" />
+          <img src="/insel-logo.png" alt="" className="logo-badge h-8 w-8 rounded-full" />
           <span className="text-lg tracking-tight text-fg">
             Handy-<span className="font-bold">Insel</span>
           </span>