Fix buttons rendering with iOS Safari's default blue chrome

globals.scss's button reset only set font: inherit — no appearance
reset, no color fallback. Several buttons only set a background and
relied on inherited text color, which iOS Safari doesn't honor for
unstyled <button> elements, so their labels/icons rendered in Safari's
native blue instead of the theme color:

- .stepperButton in MenuItemCustomizer, MenuList, and basket
- .refreshButton in admin/kitchen
- .addButton in admin/MenuItemForm (color was only set on :hover)

Added explicit `color` to each, and hardened globals.scss's button
reset with `color: inherit` plus `-webkit-appearance: none` /
`appearance: none` as a fallback for any future button that forgets.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RvYdJ3os7tumimsLdLu2j9

src/components/ordering/MenuItemCustomizer.module.scss

@@ -62,6 +62,7 @@
   border-radius: 50%;
   border: 1px solid $color-border;
   background: $color-background;
+  color: $color-text;
   cursor: pointer;
   transition: border-color 0.15s ease;