Release v0.4.0 - HD Thumbnails, YouTube 2024+ Support, and yt-dlp Integration

Major Features:
- HD video thumbnails (hq720.jpg) with automatic fallback to lower qualities
- HD channel avatars (240x240 instead of 88x88)
- YouTube 2024+ lockupViewModel support for channel playlists
- youtubei/v1/browse API integration for channel playlist tabs
- yt-dlp integration for multi-language audio and subtitles

Bug Fixes:
- Fixed undefined `abort` import in playlist.py
- Fixed undefined functions in proto.py (encode_varint, bytes_to_hex, succinct_encode)
- Fixed missing `traceback` import in proto_debug.py
- Fixed blurry playlist thumbnails using default.jpg instead of HD versions
- Fixed channel playlists page using deprecated pbj=1 format

Improvements:
- Automatic thumbnail fallback system (hq720 → sddefault → hqdefault → mqdefault → default)
- JavaScript thumbnail_fallback() handler for 404 errors
- Better thumbnail quality across all pages (watch, channel, playlist, subscriptions)
- Consistent HD avatar display for all channel items
- Settings system automatically adds new settings without breaking user config

Files Modified:
- youtube/watch.py - HD thumbnails for related videos and playlist items
- youtube/channel.py - HD thumbnails for channel playlists, youtubei API integration
- youtube/playlist.py - HD thumbnails, fixed abort import
- youtube/util.py - HD thumbnail URLs, avatar HD upgrade, prefix_url improvements
- youtube/comments.py - HD video thumbnail
- youtube/subscriptions.py - HD thumbnails, fixed abort import
- youtube/yt_data_extract/common.py - lockupViewModel support, extract_lockup_view_model_info()
- youtube/yt_data_extract/everything_else.py - HD playlist thumbnails
- youtube/proto.py - Fixed undefined function references
- youtube/proto_debug.py - Added traceback import
- youtube/static/js/common.js - thumbnail_fallback() handler
- youtube/templates/*.html - Added onerror handlers for thumbnail fallback
- youtube/version.py - Bump to v0.4.0

Technical Details:
- All thumbnail URLs now use hq720.jpg (1280x720) when available
- Fallback handled client-side via JavaScript onerror handler
- Server-side avatar upgrade via regex in util.prefix_url()
- lockupViewModel parser extracts contentType, metadata, and first_video_id
- Channel playlist tabs now use youtubei/v1/browse instead of deprecated pbj=1
- Settings version system ensures backward compatibility

youtube/ytdlp_proxy.py

@@ -17,44 +17,44 @@ logger = logging.getLogger(__name__)
 def stream_video_with_audio(video_id: str, audio_language: str = 'en', max_quality: int = 720):
     """
     Stream video with specific audio language.
-    
+
     Args:
         video_id: YouTube video ID
         audio_language: Preferred audio language (default: 'en')
         max_quality: Maximum video height (default: 720)
-        
+
     Returns:
         Flask Response with video stream, or 404 if not available
     """
     logger.info(f'Stream request: {video_id} | audio={audio_language} | quality={max_quality}p')
-    
+
     # Find best unified format
     best_format = find_best_unified_format(video_id, audio_language, max_quality)
-    
+
     if not best_format:
         logger.info(f'No suitable unified format found, returning 404 to trigger fallback')
         return Response('No suitable unified format available', status=404)
-    
+
     url = best_format.get('url')
     if not url:
         logger.error('Format found but no URL available')
         return Response('Format URL not available', status=500)
-    
+
     logger.debug(f'Streaming from: {url[:80]}...')
-    
+
     # Stream the video
     try:
         req = urllib.request.Request(url)
         req.add_header('User-Agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36')
         req.add_header('Accept', '*/*')
-        
+
         # Add Range header if client requests it
         if 'Range' in request.headers:
             req.add_header('Range', request.headers['Range'])
             logger.debug(f'Range request: {request.headers["Range"]}')
-        
+
         resp = urllib.request.urlopen(req, timeout=60)
-        
+
         def generate():
             """Generator for streaming video chunks."""
             try:
@@ -66,28 +66,28 @@ def stream_video_with_audio(video_id: str, audio_language: str = 'en', max_quali
             except Exception as e:
                 logger.error(f'Stream error: {e}')
                 raise
-        
+
         # Build response headers
         response_headers = {
             'Content-Type': resp.headers.get('Content-Type', 'video/mp4'),
             'Access-Control-Allow-Origin': '*',
         }
-        
+
         # Copy important headers
         for header in ['Content-Length', 'Content-Range', 'Accept-Ranges']:
             if header in resp.headers:
                 response_headers[header] = resp.headers[header]
-        
+
         status_code = resp.getcode()
         logger.info(f'Streaming started: {status_code}')
-        
+
         return Response(
             stream_with_context(generate()),
             status=status_code,
             headers=response_headers,
             direct_passthrough=True
         )
-        
+
     except urllib.error.HTTPError as e:
         logger.error(f'HTTP error streaming: {e.code} {e.reason}')
         return Response(f'Error: {e.code} {e.reason}', status=e.code)