fix: Add tagline to Login branding state + troubleshooting doc

admin-spa/src/routes/Login.tsx

@@ -16,6 +16,7 @@ export function Login() {
     logo: '',
     logoDark: '',
     storeName: 'WooNooW',
+    tagline: '',
   });
   const [isDark, setIsDark] = React.useState(false);
   const navigate = useNavigate();
@@ -46,6 +47,7 @@ export function Login() {
           logo: data.store_logo || '',
           logoDark: data.store_logo_dark || '',
           storeName: data.store_name || 'WooNooW',
+          tagline: data.store_tagline || '',
         });
       })
       .catch(err => console.error('Failed to load branding:', err));