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/app/(admin)/admin/queue/page.tsx

@@ -167,14 +167,14 @@ export default function AdminQueuePage() {
             onChange={(e) => setSearch(e.target.value)}
             placeholder={t("ui.searchPlaceholder")}
             aria-label={t("ui.searchPlaceholder")}
-            className="w-full rounded-[10px] border border-white/[0.14] bg-transparent py-2 pl-9 pr-3 text-[13px] text-slate-100 placeholder:text-slate-500"
+            className="w-full rounded-[10px] border border-ink/[0.14] bg-transparent py-2 pl-9 pr-3 text-[13px] text-slate-100 placeholder:text-slate-500"
           />
         </div>
         <select
           value={status}
           onChange={(e) => setStatus(e.target.value)}
           aria-label={t("common.status")}
-          className="rounded-[10px] border border-white/[0.14] bg-dark-panel px-3 py-2 text-[13px] text-slate-100"
+          className="rounded-[10px] border border-ink/[0.14] bg-dark-panel px-3 py-2 text-[13px] text-slate-100"
         >
           <option value="">{t("ui.all")}</option>
           {/* Taken from the aggregate, so the choices are the states this