feat: Together AI Primary

fix: usar Together AI y Fireworks vía HF Router, arreglar Pollinations

fix: usar api-inference.hf.co (bypass DNS de Vercel) en lugar de huggingface.co

fix: agregar x-wait-for-model y cadena de fallback de modelos HF

fix: corregir hfToken undefined y timeouts en generate-2d

fix: remove unused module import to resolve 500 error on Vercel

fix: use resilient multi-fallback FLUX generator for 2D images

feat: complete serverless migration with clean secure environment variables