feat: rename TalkTime Dashboard/Login to Talkhub in UI

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0143yYvjesjHndBACoweyK67

frontend/src/components/auth/LoginForm.tsx

@@ -48,7 +48,7 @@ export function LoginForm() {
   return (
     <Card className="w-full max-w-sm">
       <CardHeader>
-        <CardTitle>TalkTime Login</CardTitle>
+        <CardTitle>Talkhub Login</CardTitle>
       </CardHeader>
       <CardContent>
         <Form {...form}>

frontend/src/pages/DashboardPage.tsx

@@ -18,7 +18,7 @@ export function DashboardPage() {
           "Abmelden" short of horizontal scrolling. Stack on narrow screens. */}
       <div className="flex flex-col gap-4 sm:flex-row sm:items-center sm:justify-between">
         <div className="space-y-2">
-          <h1 className="text-2xl font-semibold">TalkTime Dashboard</h1>
+          <h1 className="text-2xl font-semibold">Talkhub</h1>
           {user && <p className="text-sm text-muted-foreground">Angemeldet als {user.email}</p>}
           <OrganizationSwitcher />
         </div>