Better error messages from backend, avoid bad toasts, cleanup of session validation.

frontend/src/admin/AdminApp.vue

@@ -574,10 +574,10 @@ async function submitDialog() {
     <StatusMessage />
     <main class="app-main">
       <LoadingView v-if="loading" :message="loadingMessage" />
-      <AuthRequiredMessage 
-        v-else-if="showBackMessage" 
+      <AuthRequiredMessage
+        v-else-if="showBackMessage"
         message="You need to authenticate to access the admin panel."
-        @reload="reloadPage" 
+        @reload="reloadPage"
       />
       <section v-else class="view-root view-root--wide view-admin">
         <header class="view-header">

frontend/src/components/RestrictedAuth.vue

@@ -135,7 +135,7 @@ async function authenticateUser() {
     loading.value = false
     const message = error?.message || 'Passkey authentication cancelled'
     const cancelled = message === 'Passkey authentication cancelled'
-    showMessage(cancelled ? message : `Authentication failed: ${message}`, cancelled ? 'info' : 'error', 4000)
+    showMessage(message, cancelled ? 'info' : 'error', 4000)
     emit('auth-error', { message, cancelled })
     return
   }

frontend/src/restricted-api/RestrictedApiApp.vue

@@ -4,7 +4,6 @@
     @authenticated="handleAuthenticated"
     @forbidden="handleForbidden"
     @logout="handleLogout"
-    @auth-error="handleAuthError"
     @back="handleBack"
   />
 </template>
@@ -51,15 +50,6 @@ function handleLogout() {
   })
 }
 
-function handleAuthError({ message, cancelled }) {
-  // Notify parent that authentication failed or was cancelled
-  postToParent({
-    type: 'auth-error',
-    message: message || 'Authentication failed',
-    cancelled
-  })
-}
-
 function handleBack() {
   console.log('[RestrictedApiApp] Back clicked')
   // Notify parent that user wants to go back

frontend/src/stores/auth.js

@@ -112,7 +112,7 @@ export const useAuthStore = defineStore('auth', {
         throw new Error('Authentication required')
       }
       const result = await response.json()
-      if (result.detail) throw new Error(`Server: ${result.detail}`)
+      if (result.detail) throw new Error(result.detail)
 
       await this.loadUserInfo()
     },

frontend/src/utils/awaitable-websocket.js

@@ -59,7 +59,7 @@ class AwaitableWebSocket extends WebSocket {
       throw new Error("Failed to parse JSON from WebSocket message")
     }
     if (parsed.detail) {
-      throw new Error(`Server: ${parsed.detail}`)
+      throw new Error(parsed.detail)
     }
     return parsed
   }