fix: handle serverless 404 by falling back to DialoGPT/distilgpt2; default serverless model to DialoGPT

app.py

@@ -355,7 +355,8 @@ class TextilindoAI:
         self.endpoint_url = (os.getenv('HF_ENDPOINT_URL') or '').strip()
         # Normalize model: block unsupported/gated models; prefer widely available ones
         env_model = (os.getenv('DEFAULT_MODEL') or '').strip()
-        default_supported = 'TinyLlama/TinyLlama-1.1B-Chat-v1.0'
+        # Use a widely available serverless default to avoid 404s
+        default_supported = 'microsoft/DialoGPT-medium'
         if env_model and (
             'gpt2' in env_model.lower()
             or 'meta-llama/llama-3.2-1b-instruct' in env_model.lower()
@@ -366,7 +367,8 @@ class TextilindoAI:
         else:
             # Safer default
             self.model = env_model or default_supported
-        self._fallback_model = default_supported
+        # Fallback model used on serverless 404s
+        self._fallback_model = 'distilgpt2'
         self.system_prompt = self.load_system_prompt()
         self.data_loader = TrainingDataLoader()