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/templates/channel.html

@@ -81,10 +81,10 @@
         <!-- new-->
         <div id="links-metadata">
                 {% if current_tab in ('videos', 'shorts', 'streams') %}
-                    {% set sorts = [('1', 'views'), ('2', 'oldest'), ('3', 'newest'), ('4', 'newest - no shorts'),] %}
+                    {% set sorts = [('3', 'newest'), ('4', 'newest - no shorts')] %}
                     <div id="number-of-results">{{ number_of_videos }} videos</div>
                 {% elif current_tab == 'playlists' %}
-                    {% set sorts = [('2', 'oldest'), ('3', 'newest'), ('4', 'last video added')] %}
+                    {% set sorts = [('3', 'newest'), ('4', 'last video added')] %}
                     {% if items %}
                         <h2 class="page-number">Page {{ page_number }}</h2>
                     {% else %}