Fix dark-background text contrast and flatten all button appearances Several Text/NumberControl-title nodes in the Analyzer and Photometry screens sit directly on the dark default screen background (their containing columns aren't wrapped in a light panel like the other screens) but used the default black fill or panelTextColorProperty / mutedTextColorProperty, which are meant for light panel surfaces — making them invisible in the default color profile. Switched those to textColorProperty. Registration and Blink Comparator were already correct (light panel/table backgrounds throughout). Also added src/common/VSPButtonOptions.ts (mirroring RotatingSky's pattern) with a shared FlatAppearanceStrategy bundle, and applied it to every RectangularPushButton/TextPushButton/ResetAllButton call site across all four screens so buttons #9