fix(login): unify auth entry to single keycloak login page

frontend/src/pages/LoginPage.vue

@@ -48,7 +48,7 @@
       </el-button>
 
       <div class="mt-4 text-xs text-gray-400 text-center space-y-1">
-        <p>登入會跳轉到 Authentik 驗證，完成後自動返回。</p>
+        <p>登入會統一跳轉到 Keycloak 登入頁，完成後自動返回。</p>
         <p>登入成功後 access token 會存於本機 localStorage。</p>
       </div>
     </el-card>
@@ -97,10 +97,8 @@ async function handleOidcLogin() {
   oidcLoading.value = true
   error.value = ''
   try {
-    const googleIdpHint = import.meta.env.VITE_OIDC_IDP_HINT_GOOGLE || undefined
     await redirectToOidc({
-      prompt: 'select_account',
-      idpHint: googleIdpHint
+      prompt: 'login'
     })
   } catch (err) {
     error.value = err.message || '登入失敗，請稍後再試'