fix(byok): add xai settings UI row

xai is both hosted (Pi block hides its inline API key field for
hosted models) and Pi-supported (cloud mode requires a user key),
so without a Settings > BYOK row users had no way to supply an xai
key for Pi cloud runs.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/settings/components/byok/byok.tsx

@@ -33,6 +33,7 @@ import {
   SerperIcon,
   TogetherIcon,
   WizaIcon,
+  xAIIcon,
   ZeroBounceIcon,
 } from '@/components/icons'
 import { MAX_BYOK_KEYS_PER_PROVIDER } from '@/lib/api/contracts/byok-keys'
@@ -75,6 +76,13 @@ const PROVIDERS: (BYOKManagerProvider & { id: BYOKProviderId })[] = [
     description: 'LLM calls and Knowledge Base OCR',
     placeholder: 'Enter your API key',
   },
+  {
+    id: 'xai',
+    name: 'xAI',
+    icon: xAIIcon,
+    description: 'LLM calls',
+    placeholder: 'xai-...',
+  },
   {
     id: 'fireworks',
     name: 'Fireworks',
@@ -279,6 +287,7 @@ const PROVIDER_SECTIONS: BYOKProviderSection[] = [
       'anthropic',
       'google',
       'mistral',
+      'xai',
       'fireworks',
       'together',
       'baseten',