Refactor login error handling and improve user feedback

- Update LoginForm component to display error messages directly from the authentication response.
- Modify useAuth composable to handle login errors more effectively, ensuring proper error messages are thrown.
- Enhance login API response to return structured error messages for invalid credentials.
- Adjust Cidaas utility to throw specific errors for invalid username/password scenarios.

app/composables/useAuth.ts

@@ -17,26 +17,32 @@ export function useAuth() {
    * Direct authentication via Cidaas API (no redirect)
    */
   async function login(email: string, password: string) {
-    try {
-      // Call login endpoint - creates session directly
-      await $fetch('/api/auth/login', {
-        method: 'POST',
-        body: { email, password },
-      })
+    // Call login endpoint - creates session directly
+    const response = await $fetch<{ success: boolean; message?: string }>('/api/auth/login', {
+      method: 'POST',
+      body: { email, password },
+      // Don't throw on 4xx/5xx, we handle the response ourselves
+      ignoreResponseError: true,
+    })
 
-      // Refresh user session
-      await fetch()
-
-      // Redirect to homepage or saved destination
-      const redirectAfterLogin = useCookie('redirect_after_login')
-      const destination = redirectAfterLogin.value || '/'
-      redirectAfterLogin.value = null // Clear cookie
-
-      navigateTo(destination)
-    } catch (error) {
-      console.error('Login failed:', error)
+    // Check if login was successful
+    if (!response.success) {
+      // Throw error with the server's message (contains German text with umlauts)
+      const error: any = new Error(response.message || 'Login failed')
+      error.data = response
+      error.statusCode = 401
       throw error
     }
+
+    // Refresh user session
+    await fetch()
+
+    // Redirect to homepage or saved destination
+    const redirectAfterLogin = useCookie('redirect_after_login')
+    const destination = redirectAfterLogin.value || '/'
+    redirectAfterLogin.value = null // Clear cookie
+
+    navigateTo(destination)
   }
 
   /**