[FEAT] Make EXIF panel movable & improve HEIC preview speed

[Timwang886]

Hi there,

Thanks a lot for building such a lightweight and fast image viewer. It’s quickly become my go-to tool for checking photos, especially RAW files.

I have two small feature suggestions:

1. The EXIF info panel in the top-left corner is currently fixed, and sometimes it blocks parts of my photos when I’m viewing them. It would be really helpful if this panel could be dragged and moved to any position on the screen.
2. I also noticed that previewing HEIC photos takes noticeably longer than other formats. It would be great if the loading speed for HEIC could be optimized a bit.

Thanks again for your work on this project!