fix(ui): fix keyboard shortcuts modal Enter key emoji and menu capitalization (#26173)

- Append Unicode text variation selector U+FE0E to the ↩ character in
  ShortcutItem.svelte to prevent iOS/iPadOS rendering it as a colorful
  emoji instead of a plain text glyph.
- Fix 'Keyboard shortcuts' → 'Keyboard Shortcuts' (capital S) in the
  user menu to match the modal title and standard title case.

src/lib/components/chat/ShortcutItem.svelte

@@ -46,7 +46,7 @@
 			case 'escape':
 				return 'Esc';
 			case 'enter':
-				return isMac ? '↩' : 'Enter';
+				return isMac ? '↩\uFE0E' : 'Enter';
 			case 'tab':
 				return isMac ? '⇥' : 'Tab';
 			case 'arrowup':