Implement Carlos' suggestions for improvements

[logan-nc]

General GUI:

• Larger GUI font size

Quasi-stationary

• Break out all quasi-stationary mode raw sensors into own plots
• Check boxes to deselect sensors used in fits
• Ability to plot user desired signal vs time next to primary plots (eg Ip , dalpha, etc.)

Rotating modes

• ID even / odd modes on spectrogram
• Color spectrogram by Eigespec "feature index" rather than toroidal mode number (will distinguish between 1/1, 2/1, 3/1 etc.)
• Ability to plot user desired signal vs time next to primary plots (eg Ip , dalpha, etc.)
• Arbitrary signal spectrogram below the magnetics one for comparison
• Match modespec colors for n modes
• Cross correlation plots

New tabs:

• Combine amplitude plots from slow and rotating

[logan-nc]

FYI I am doing the QS items

[logan-nc]

PR #71 (into develop) addresses two items from this list:

• General GUI → Larger GUI font size — adds a header gear-icon Appearance menu (housing the light/dark toggle + an S / M / L / XL text-size control). Text size is a global --font-scale multiplier that rescales the whole app's typography, including the per-tab inline label/control sizes. Presets span evenly from S (0.85) to a boosted XL (1.6).
• Rotating modes → Match modespec colors for n modes — recolors the discrete n-mode palette warm→cool so 1=red, 2=orange, 3=yellow, then green/blue/purple (0=grey = "no mode"). Shared palette, so the rotating spectrogram and any discrete n-map stay consistent.

I've checked both boxes above. The remaining items are untouched (a couple — QS raw-sensor breakout, spectrogram signal comparisons — are being handled on other branches).