feat: add Impressum and Datenschutz links on login page

Legal links shown below the login card, opening iframe dialog
to keep users on the page.

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

frontend/src/pages/LoginPage.tsx

@@ -5,6 +5,9 @@ import { z } from 'zod'
 import { useNavigate } from 'react-router-dom'
 import { useAuth } from '@/context/AuthContext'
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
+import {
+  Dialog, DialogContent, DialogHeader, DialogTitle,
+} from '@/components/ui/dialog'
 import { Input } from '@/components/ui/input'
 import { Button } from '@/components/ui/button'
 import { Label } from '@/components/ui/label'
@@ -27,6 +30,7 @@ export function LoginPage() {
   const [error, setError] = useState<string | null>(null)
   const [showMfa, setShowMfa] = useState(false)
   const [isSubmitting, setIsSubmitting] = useState(false)
+  const [legalDialog, setLegalDialog] = useState<{ title: string; url: string } | null>(null)
 
   const {
     register,
@@ -150,6 +154,35 @@ export function LoginPage() {
           </form>
         </CardContent>
       </Card>
+
+      <div className="mt-4 flex items-center gap-3 text-xs text-muted-foreground">
+        <button
+          onClick={() => setLegalDialog({ title: 'Impressum', url: 'https://complexcaresolutions.de/impressum/' })}
+          className="hover:text-foreground underline underline-offset-2 transition-colors"
+        >
+          Impressum
+        </button>
+        <span>·</span>
+        <button
+          onClick={() => setLegalDialog({ title: 'Datenschutzerklärung', url: 'https://www.complexcaresolutions.de/datenschutzerklaerung/' })}
+          className="hover:text-foreground underline underline-offset-2 transition-colors"
+        >
+          Datenschutz
+        </button>
+      </div>
+
+      <Dialog open={!!legalDialog} onOpenChange={(open) => { if (!open) setLegalDialog(null) }}>
+        <DialogContent className="max-w-4xl h-[85vh] flex flex-col p-0">
+          <DialogHeader className="px-6 pt-6 pb-2">
+            <DialogTitle>{legalDialog?.title}</DialogTitle>
+          </DialogHeader>
+          <iframe
+            src={legalDialog?.url}
+            className="flex-1 w-full border-0 rounded-b-lg"
+            title={legalDialog?.title}
+          />
+        </DialogContent>
+      </Dialog>
     </div>
   )
 }