Add Header unsubscribe function on mount

src/routes/Header.svelte

@@ -7,16 +7,24 @@
     let username = null;
     let profileTitle = null;
 
-    $: auth.subscribe(value => {
+    const unsubscribe = auth.subscribe(value => {
         username = value ? value.username : "";
-        profileTitle = value ? "You are logged in as " + value.username : "login";
+        profileTitle = value ? `You are logged in as ${value.username}` : "Login";
     });
 
     onMount(() => {
         const storedAuth = localStorage.getItem('auth');
         if (storedAuth) {
-            auth.set(JSON.parse(storedAuth));
+            try {
+                auth.set(JSON.parse(storedAuth));
+            } catch (e) {
+                console.error("Failed to parse auth from localStorage", e);
+            }
         }
+
+        return () => {
+            unsubscribe();
+        };
     });
 
 </script>