### Changes
Replace hard-coded plan checks with `assistant.advance_model`
entitlement for AI model access control.
- `AIAssistant.tsx` & `ModelSelector.tsx`: Use
`useCheckEntitlements('assistant.advance_model')` instead of `plan.id
!== 'free'`
**Server-side:**
- `org-ai-details.ts`: Check `assistant.advance_model` entitlement via
new `checkEntitlement()` helper
- `entitlements-query.ts`: Add `checkEntitlement()` function with auth
headers support for server-side calls
### Test 1: Free Plan (No Entitlement)
- Open AI Assistant with a Free plan org
- Check model selector defaults to gpt-5-mini
- Click dropdown - verify gpt-5 shows "Upgrade" badge
- Click gpt-5 - should redirect to billing page
- Assert that you can send a message to the Assistant and that you get a
response
<img width="335" height="156" alt="image"
src="https://github.com/user-attachments/assets/2458cbd1-46ab-46cd-babb-09a47e163fd0"
/>
### Test 2: Paid Plan (Has Entitlement)
- Switch to Pro/Team/Enterprise org
- Check model selector defaults to gpt-5
- Click dropdown - verify gpt-5 shows checkmark (no badge)
- Switch to gpt-5-mini, then back to gpt-5 - should work without
redirect
- Assert that you can send a message to the Assistant and that you get a
response
* Add custom types for queries, mutations and infinite queries.
* Migrate all queries to use the new type.
* Migrate all infinite queries to useCustomInfiniteQueryOptions.
* Migrate all mutations to use useCustomMutationOptions.
* Add type to all imports in `types` folder.
