Add missing download_file method to OmniAvatarAPI

CRITICAL FIX: Added missing download_file method that was causing AttributeError
- async def download_file(url, suffix) -> str
- Downloads files from URLs to temporary locations using aiohttp
- Handles HTTP errors and file creation
- Returns temporary file path for processing
- Used by generate_avatar for downloading audio and image files
- Includes proper error handling and logging

This fixes: 'OmniAvatarAPI' object has no attribute 'download_file'

app_main.py

@@ -318,6 +318,32 @@ class OmniAvatarAPI:
                     logger.info(f"? SUCCESS: Downloaded models loaded - Video: {video_files}, Audio: {audio_files}")
                     return True
 
+    async def download_file(self, url: str, suffix: str = '') -> str:
+        """Download file from URL to temporary location"""
+        import aiohttp
+        import tempfile
+        import os
+        
+        try:
+            async with aiohttp.ClientSession() as session:
+                async with session.get(url) as response:
+                    if response.status != 200:
+                        raise Exception(f"Failed to download {url}: HTTP {response.status}")
+                    
+                    # Create temporary file with appropriate suffix
+                    with tempfile.NamedTemporaryFile(suffix=suffix, delete=False) as tmp_file:
+                        content = await response.read()
+                        tmp_file.write(content)
+                        temp_path = tmp_file.name
+                    
+                    logger.info(f"Downloaded {len(content)} bytes from {url} to {temp_path}")
+                    return temp_path
+                    
+        except Exception as e:
+            logger.error(f"Failed to download file from {url}: {e}")
+            raise HTTPException(status_code=400, detail=f"Failed to download file: {e}")
+
+
             # Fallback: Check traditional OmniAvatar paths
             traditional_paths = [
                 "./pretrained_models/Wan2.1-T2V-14B",