fix(front): pass auth headers to GraphiQL fetcher for introspection (#21821)

## Summary
https://discord.com/channels/1130383047699738754/1517429151328374896
- The GraphiQL playground's automatic introspection query was firing
without an `Authorization` header, causing "GraphQL introspection has
been disabled" errors in production
- `defaultHeaders` only pre-fills the GraphiQL headers editor UI — it
does not inject headers into actual fetch requests
- Added `headers` to the `createGraphiQLFetcher` config so all requests
(including auto-introspection on load) are authenticated


## Test plan

- [x] Open Settings > API & Webhooks, select Core schema + GraphQL,
click Launch
- [x] Verify the introspection query in the network tab now includes the
`Authorization: Bearer ...` header
- [x] Confirm the schema explorer loads successfully in a production
environment (or with `NODE_ENV=production`)

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packages/twenty-front/src/modules/settings/playground/components/GraphQLPlayground.tsx

@@ -55,6 +55,9 @@ export const GraphQLPlayground = ({
 
   const fetcher = createGraphiQLFetcher({
     url: baseUrl,
+    headers: {
+      Authorization: `Bearer ${playgroundApiKey.token}`,
+    },
   });
 
   return (