Compose: close on Send and offer Undo from a toast; phone-size touch targets

Clicking Send now closes the compose window right away. The undo offer moved
out of the composer into a toast: bottom right on a desktop, a small "Undo"
pill with the countdown bottom left on a phone, where sending also returns to
the message list. An undone send reopens the draft in a composer. The
popped-out compose window keeps its inline undo bar, since closing it would
lose the offer.

Also: drop the "Reply" label from the From row; on a phone show the Send
button as its icon alone, enlarge the Send/Attach/Close icons by half, put the
logo beside the menu button, make the reading view's back arrow bolder, and
make the list's pagination bar half again as big.

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

frontend/src/i18n/en.ts

@@ -212,7 +212,6 @@ export const en = {
   "compose.expand": "Expand",
   "compose.collapse": "Collapse",
   "compose.popOut": "Pop out",
-  "compose.replyLabel": "Reply",
   "compose.addRecipient": "Add recipient…",
   "compose.fmtBold": "Bold",
   "compose.fmtItalic": "Italic",