[supernova-jpg]

Summary

YUView previously quantized all image files down to 8-bit RGB upon loading via Qt's standard reader. This PR introduces native high-bit-depth image decoding for:

• 16-bit PNG images (QImage::Format_Grayscale16 and QImage::Format_RGBA64) with full scanline unfiltering (Sub, Up, Average, Paeth) and IDAT decompression.
• 48-bit / 64-bit uncompressed BMP images.

Key Additions

1. Lossless 16-Bit Image Loader:
   • loadImagePreservingHighBitDepth() reads raw 16-bit samples without quantizing to 8-bit.
2. Analytical Pixel Value Inspection:
   • Pixel value inspection tooltips and difference calculations now show the true high-bit-depth sample values (up to 65535, or scaled to 10-bit 1023).
3. Properties Widget Integration:
   • Added a bit depth selector (16-bit vs 10-bit mode) in the Image Properties panel of playlistItemImageFile.

Testing & Regressions

• Tested with 16-bit PNG (grayscale and RGBA) and standard 8-bit PNG/JPEG/BMP files.
• Standard 8-bit images continue using the fast path with zero performance penalty.