Guide Feishu app setup and surface tenant lookup codes

frontend/src/locales/en-US.json

@@ -575,6 +575,7 @@
   },
   "identity": {
     "tab": "Feishu identity", "title": "Built-in Feishu identity service", "description": "Issue OIDC identities for VPN using your existing HTTPS domain. Feishu app credentials stay upstream; this platform creates separate VPN client credentials.",
+    "guideTitle": "Configure your Feishu app", "guideApp": "In Feishu Open Platform → Enterprise apps, open your app. Copy the App ID and App Secret from Credentials & Basic Information into the fields below. Use enterprise app credentials.", "guidePermission": "In Permissions, request read access to enterprise information (search for tenant:tenant:readonly or 'get enterprise information'; use the actual name shown by Feishu) for automatic tenant lookup. Allow the user_profile scope for browser sign-in user info.", "guidePublish": "Publish or enable the new app version, complete administrator review if required, and add VPN users to the app's availability scope. Creating the app or adding a permission alone does not activate it.", "guideCallback": "In Security Settings → Redirect URLs, add this exact Feishu sign-in callback:", "guideCallbackPending": "Configure the HTTPS domain under Public Gateway first to see the callback URL.", "guideVerify": "Save and enable the identity service here, then sync its public routes and try a user in the app's availability scope. The Feishu callback differs from the VPN client callback below.", "guideManual": "If automatic lookup fails, enter a tenant_key verified from user information in the same enterprise. The Feishu error code appears below the field; retry after changing credentials or permissions.",
     "appId": "Feishu App ID", "appSecret": "Feishu App Secret", "secretPlaceholder": "Leave blank to retain the secret; use a rotated secret for new setup", "tenant": "Allowed Feishu tenant_key", "tenantPlaceholder": "Fetch automatically or enter manually", "fetchTenant": "Fetch tenant ID", "tenantFetched": "Feishu tenant ID retrieved", "tenantFailed": "Could not fetch Feishu tenant", "enabled": "Enable built-in issuer", "httpsOnly": "Enter app credentials only through the HTTPS management site. Switch to its secure address.", "openHttps": "Open HTTPS management site",
     "httpsRequired": "Configure and activate your public HTTPS site and certificate first.", "gatewayPending": "The identity provider is saved but Nginx does not yet route /id/; sync the gateway.",
     "addresses": "Addresses and client credentials", "issuer": "OIDC issuer", "feishuCallback": "Callback registered in Feishu", "vpnCallback": "VPN client callback", "clientId": "VPN Client ID",