Simplified the FLAC pk collision fix to work uniformly for all files:
- Always read up to 1024 bytes (or whatever is available)
- Use at most the last 512 bytes for pk calculation
This approach works correctly for:
- Small files (< 512 bytes, e.g., tiny images): uses all content
- Medium files (512-1024 bytes): uses bytes after 512
- Large files (>= 1024 bytes, e.g., FLAC): uses bytes 512-1024
No special detection needed - the algorithm adapts automatically.
Fixes potential issues with small images in pmocovers cache.
64586721b9