Theme menu: the same palettes as INBUXA webmail

Under the user menu, Theme offers ihasmail's palettes, in the same order and
under the same names. ihasmail is the default look, the colors the admin
already had, until someone picks another. The choice is remembered and
applied before the first paint, and dark mode still toggles on its own.

The other palettes' colors are ihasmail's, already contrast-checked, mapped
onto the admin's tokens by scripts/import-palettes.py; re-running it re-syncs
them. NOTICE carries the palettes' MIT notices and the fonts' OFL notices.

src/main.tsx

@@ -27,6 +27,11 @@ import { loadLogoOnce } from './lib/logoCache';
     if (persisted) {
       const parsed = JSON.parse(persisted);
       const theme = parsed?.state?.theme;
+      // INBUXA: the palette too, before the first paint, so it doesn't flash.
+      const palette = parsed?.state?.palette;
+      if (typeof palette === 'string' && palette !== 'ihasmail' && /^[a-z-]+$/.test(palette)) {
+        document.documentElement.dataset.palette = palette;
+      }
       if (theme === 'dark' || theme === 'light') {
         document.documentElement.classList.toggle('dark', theme === 'dark');
         return;