fix(models): mark OpenAI gpt-4.1-nano deprecated (#9340)

OpenAI retired gpt-4.1-nano and the API now returns 404, so move it from legacy to deprecated: hidden from model pickers, still a known id so pinned workflows validate.

Author: waleedlatif1

apps/sim/providers/models.ts

@@ -705,7 +705,7 @@ export const PROVIDER_DEFINITIONS: Record<string, ProviderDefinition> = {
         },
         contextWindow: 1047576,
         releaseDate: '2025-04-14',
-        sunset: { status: 'legacy' },
+        sunset: { status: 'deprecated' },
       },
       // GPT-5.6 family
       {