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/layout/Sidebar/UserMenu.svelte

@@ -613,7 +613,7 @@
 					<div class=" self-center mr-3">
 						<Keyboard className="size-5" />
 					</div>
-					<div class=" self-center truncate">{$i18n.t('Keyboard shortcuts')}</div>
+					<div class=" self-center truncate">{$i18n.t('Keyboard Shortcuts')}</div>
 				</button>
 			{/if}