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/messages/es.json

@@ -564,5 +564,27 @@
     "draftDiscarded": "Respuesta descartada",
     "sentReply": "Respuesta enviada",
     "moreMessages": "Mostrar {count} mensajes anteriores"
+  },
+  "appearance": {
+    "title": "Apariencia",
+    "dark": "Oscuro",
+    "light": "Claro",
+    "system": "Sistema"
+  },
+  "palette": {
+    "placeholder": "Escribe un comando, una carpeta o algo que buscar",
+    "empty": "Sin resultados. Pulsa Enter para buscar esto en tu correo.",
+    "searchFor": "Buscar \"{query}\" en el correo",
+    "goTo": "Ir a {name}",
+    "actions": "Acciones",
+    "navigate": "Ir a",
+    "theme": "Apariencia",
+    "accounts": "Cuentas",
+    "switchTo": "Cambiar a {email}",
+    "hintMove": "mover",
+    "hintOpen": "abrir",
+    "hintClose": "cerrar",
+    "open": "Menú de comandos",
+    "signOut": "Cerrar sesión"
   }
 }