feat(mpv): video output levels override

[plyrthn]

Summary

Adds a "Video Levels" setting (Auto/Limited/Full) that overrides mpv's
auto-detected output color range. Auto trusts the source file's tagged
range, same as today; Limited/Full let you force it if content looks washed
out or crushed on a given display regardless of what the file is tagged as.

Files: views/Settings.qml, src/player/MpvController.cpp

P.S. I'm sorry for the 5 PRs I just felt it was better to do each feature as a single PR :)

Testing

• Platform(s) tested: Raspberry Pi 5 (Full KMS)
• Display / output tested: CRT via S-Video

Confirmed each of the three options changes mpv's output range as expected.
Not tested on macOS.

Checklist

• Changes work with remote-only navigation (up/down/left/right, enter, esc/backspace)
• Handled sizing and positioning using the root.sh & root.sw properties (did not hardcode pixels) and kept CRT overscan in mind
• Did not add tracking or analytics; only wrote settings to the local data directory if the change required storage
• Follows the patterns in ARCHITECTURE.md and the principles in CONTRIBUTING.md

[anthonycaccese]

thank you @plyrthn!

re: "P.S. I'm sorry for the 5 PRs I just felt it was better to do each feature as a single PR "
no need to apologize, this is great for me, I prefer focused clearly scoped PRs like these so it am all about it =)

I'll apologize right back though because i'll not likely get time to review each of these till some time this weekend. I hope that's ok and thank you working on these. Sorry for my delay.

[plyrthn]

Hey no worries!! Take your time friend!!! :) I LOVE this project and it looks like a DREAM on my trinitron!