Refactor encoding handling

[mrhx01]

Changes

1. Added @fix_encoding decorator

• Eliminates duplicate encoding logic in _title, _copyright, and _explanation functions
• Provides centralized error handling and logging for encoding issues
• Reduces code duplication by ~40 lines

2. Removed global video_thumb from _get_thumbs

• Replaced global variable with local variable
• Fixes potential race condition and makes function thread-safe

3. Modernized string formatting

• Changed "%sap%s.html" % (BASE, date_str) to f-string f"{BASE}ap{date_str}.html"