feat(quick-261022-k9k): Esc, slash and help shortcuts, settings, account and modal save keys

- '?' help dialog (ShortcutHelpDialog) listing the current screen's shortcuts
- Esc = Cancel on record forms; '/' focuses the list search
- settings forms: Save and close (Ctrl/Cmd+Enter, then /settings) and Ctrl/Cmd+S
- My account: Ctrl/Cmd+S
- modal forms: Ctrl/Cmd+S and Ctrl/Cmd+Enter submit the innermost dialog only
- docs: Keyboard shortcuts section in the admin SPA page

admin/src/views/FormView.vue

@@ -691,7 +691,7 @@ void load()
         {{ t('backend::lang.form.delete') }}
       </Button>
       <div class="ml-auto flex items-center gap-2.5">
-        <Button variant="ghost" data-action="cancel" @click="onLeave">{{ t('backend::lang.form.cancel') }}</Button>
+        <Button variant="ghost" data-action="cancel" hotkey="escape" @click="onLeave">{{ t('backend::lang.form.cancel') }}</Button>
         <Button
           v-if="mode === 'create'"
           variant="outline"