Revert: Keep sd.cpp fallback available for all models when diffusers fails

- Removed the GGUF-only restriction on sd.cpp fallback
- Some HF models may be GGUF even without 'gguf' in the name
- Let sd.cpp attempt loading and fail gracefully if incompatible
- This allows sd.cpp to work as a proper fallback for any model type

codai/api/images.py

@@ -534,17 +534,11 @@ async def create_image_generation(request: ImageGenerationRequest, http_request:
             print(f"Traceback: {traceback.format_exc()}")
             print(f"Trying stable-diffusion-cpp-python...")
     
-    # Try stable-diffusion-cpp-python (sd.cpp) as fallback - ONLY for GGUF models
-    # sd.cpp only works with GGUF models, not diffusers models
-    is_potential_gguf_model = (model_to_use.endswith('.gguf') or 'gguf' in model_to_use.lower() or
-                              (model_to_use.startswith('http') and '.gguf' in model_to_use) or
-                              (not model_to_use.startswith('http') and '/' in model_to_use))  # HF model IDs might be GGUF
-
-    if not is_potential_gguf_model:
-        print(f"Model '{model_to_use}' is not a GGUF model (sd.cpp only supports GGUF), skipping sd.cpp fallback")
-        sd_model = None
-    else:
-        # Try stable-diffusion-cpp-python (sd.cpp) as fallback for GGUF models
+    # Try stable-diffusion-cpp-python (sd.cpp) as fallback when diffusers fails
+    # sd.cpp works with GGUF models, but some HF models may be GGUF even without "gguf" in name
+    # Let sd.cpp attempt loading and fail gracefully if it's not compatible
+
+    # Try stable-diffusion-cpp-python (sd.cpp) as fallback
     # First, check all available image models to find one loaded via sd.cpp
     # Always check for cached models - allows dynamically loaded models to be reused across requests
     sd_model = None