feat(webmail): the new interface - logo, dark and light themes, command menu

A mark (a lambda on an ultramarine tile with the flap of an envelope), the
favicon, home-screen icons and an install manifest. Every colour is a variable
defined once per theme, and the Tailwind scales the screens already use read
them, so dark (the default) and light are a change of values and not of
classes. Geist is served by the app itself. Ctrl+K opens a command menu for
folders, actions, accounts and appearance, and typing something that matches no
command searches the mail; c writes a message and / goes to the search field.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

services/webmail/src/components/ui/Button.tsx

@@ -30,11 +30,11 @@ export function Button({
 
   const variants = {
     primary:
-      'border-indigo-500 text-indigo-500 bg-transparent hover:bg-indigo-500/[0.12] active:bg-indigo-500/[0.22]',
+      'border-transparent bg-fill text-white shadow-sm hover:bg-fill-hover active:brightness-95',
     secondary:
-      'border-white/[0.14] text-slate-100 bg-transparent hover:bg-white/[0.07] active:bg-white/[0.14]',
+      'border-ink/[0.14] text-slate-100 bg-transparent hover:bg-ink/[0.07] active:bg-ink/[0.14]',
     outline:
-      'border-white/[0.14] text-slate-300 bg-transparent hover:text-slate-100 hover:bg-white/[0.07] active:bg-white/[0.14]',
+      'border-ink/[0.14] text-slate-300 bg-transparent hover:text-slate-100 hover:bg-ink/[0.07] active:bg-ink/[0.14]',
     danger:
       'border-rose-400 text-rose-400 bg-transparent hover:bg-rose-400/[0.12] active:bg-rose-400/[0.22]',
     ghost: