feat: add settings to adjust bitrate/quality

[jsattler]

The default bitrate settings were too low.
With this commit we let users control the
quality of the recordings for H264 and HEVC.

[bodhibyte]

Thanks for developing this, I'm looking forward to bitrate / quality control.

I've been testing out v2026.2.1 (f684074) and noticed the file sizes are quite large (approx. 90MB–200MB per minute), even when selecting H.265.

I ran ffprobe on a recording and found two main drivers for this:

1. Retina Scaling: I recorded on a screen set to 1024x666, but the output video is 2048x1332. The app seems to be capturing the physical pixels rather than the logical resolution.
2. High Bitrate: The encoder is targeting ~9 Mbps, which is very high for screen capturing.

It would be incredibly helpful to also have resolution options e.g. a toggle to record at "Logical Resolution" (1x) instead of Native/Retina (2x) to save processing power and space.

Here is a snippet of the ffprobe output for context:

Stream #0:0... Video: hevc... 2048x1332, 8627 kb/s

[jsattler]

@bodhibyte thanks for your input. I added three quality modes (low, medium, high) for now. The logical vs. native resolution is something to tackle in another PR, but it's on my list as well.