implemented user login.

next: find a solution for routing

frontend/src/Components/Footer.svelte

@@ -0,0 +1,6 @@
+<script>
+    import { t } from '../translations.svelte.js';
+</script>
+<footer>
+    {@html t('footer.message','<a href="https://srsoftware.de">SRSoftware</a>')}
+</footer>

frontend/src/Components/Homepage.svelte

@@ -2,4 +2,4 @@
     import { t } from '../translations.svelte.js';
     import { user } from '../user.svelte.js';
 </script>
-<h1>{t('home.Welcome')}, {user.username}</h1>
+<h1>{t('home.Welcome',user.name)}</h1>

frontend/src/Components/Menu.svelte

@@ -3,11 +3,13 @@
     import { user } from '../user.svelte.js';
 
     function logout(){
-        user.username = null;
+        user.name = null;
     }
 </script>
 <nav>
     <a href="/">{t('nav.Home')}</a>
     <a href="https://svelte.dev/tutorial/svelte/state" target="_blank">{t('nav.Tutorial')}</a>
+    {#if user.name }
     <a href="#" on:click={logout}>Logout</a>
+    {/if}
 </nav>