Speak the editor in each person's Home Assistant language: every text in the editor section of en.json, the mockup in the screens' language, and one Language & region card for all screens

- vue-i18n 11 with the Composition API: English comes with the page, any other language loads the first time it is
  needed from screen_manager/translations, and a text a language lacks shows in English. The build keeps only _meta
  and editor of each file (vite.config.ts), never the screens' or the add-on's texts.
- The editor follows the language of the user's Home Assistant profile (<html lang> of Home Assistant's page), else
  the browser's; plural forms follow the file's _meta.plural, with the screens' rules.
- Every request tells the add-on the editor's language (X-ESP-Screens-Language), so its own words can follow it.
- The mockup draws the screens' words (Unavailable, Page 2 ›, the date, "5 min ago") in the screens' language, with
  their clock and number format.
- Settings → Language & region: the screen language, time format and number format for every screen, with the user's
  own profile offered when it differs. The per-screen clock choice goes; the top bar points there. A screen that
  still needs the new language says so in its update badge.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_tap_actions.py

@@ -226,7 +226,9 @@ class Editor(unittest.TestCase):
         self.PICKER = editor_sources.component('ActionPicker')
 
     def test_perform_action_is_a_tap_choice_with_home_assistants_list(self):
-        self.assertIn('list.push(["action", "Perform action"]);', self.SCRIPT)
+        import editor_sources
+        self.assertIn('keys.push("action");', self.SCRIPT)
+        self.assertEqual(editor_sources.text('tile.tap.action'), 'Perform action')
         self.assertIn('getJson(`entity-actions?entity=${encodeURIComponent(entity)}`)', self.SCRIPT)
         self.assertIn('<ActionPicker v-if="domain !== \'screen\' && !goesTo && tap === \'action\'" :tile="tile" />', self.SCRIPT)
         # Fields follow Home Assistant's selectors; an empty field is left out of the data.