feat: scale panel button font size with window size

[shaozk]

Before submitting a pull request:

• Did you fork from the development branch? yes
• Are you submitting the pull request to the development branch? (not master) yes

Summary

• Panel button fonts now scale with the window size instead of a fixed 20pt size
• Font size ranges from baseFontSize (20) to maxFontSize (50), based on the smaller window dimension (reference: 800px)
• Adds a resizeEvent handler that updates all panel button fonts on window resize
• Hard-coded font-size: 20pt removed from the dark/light mode stylesheets (font now set via QFont on the label)

Changes

• src/panelgenerator.h: add static font constants, panelButtons list, panelFontSize()/updatePanelFonts() methods, and resizeEvent() override
• src/panelgenerator.cpp: implement font scaling, track buttons via panelButtons, clear the list in clearLayout(), and recalc fonts on resize

Notes

• Co-Authored-By: opencode-agent[bot] <opencode-agent[bot]@users.noreply.github.com>

[dannagle]

Qt supports a global zoom factor with the environment variable QT_SCALE_FACTOR. I was once considering looking into ways to support that. Did you ever attempt that in your testing?

Your tweak should scale along with that zoom factor.