fix: widgets too small / cropped on macOS (workbench + workflow config)

[pecomyint]

Problem

Several buttons, spinboxes, and combo boxes are too small or have cropped text on macOS. Likely also affects some Linux desktop environments. Root cause: missing minimum size constraints and very tight padding in .ui files.

Affected widgets

Workbench (workbench.ui)

Widget	Name	Issue
Vmin/Vmax spinboxes	sbVmin, sbVmax	No minimumSize, too thin on macOS
Color map dropdown	cbColorMapSelect_2d	No minimumSize
Frame prev/next buttons	btn_prev_frame, btn_next_frame	maxWidth: 30px, no min-height, arrow text "◀▶" gets clipped

PVA Workflow Setup config tab (workflow.ui)

Widget	Name	Issue
Refresh button	buttonRefreshDb	padding: 1px 6px — too tight
Expand All / Collapse All	buttonExpandAll, buttonCollapseAll	maxWidth: 32px, padding: 1px 6px
Add Top Level Key	buttonAddTopLevel	maxWidth: 60px, padding: 1px 8px, font-size: 8pt

Global theme (theme.qss)

• No generic QComboBox or QPushButton min-height rules

Proposed fix

1. Add min-height: 28px to generic QComboBox and small QPushButton in theme.qss
2. Increase padding on tight buttons from 1px 6px → 4px 8px
3. Bump maxWidth on frame nav buttons from 30px → 36px
4. Add explicit minimumHeight to spinboxes and combo boxes in workbench.ui
5. Test on macOS and Linux

Context

Reported during dev-peco branch testing. Separate from the color centralization work.