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_editor_live.py

@@ -225,10 +225,12 @@ class Editor(unittest.TestCase):
         for marker in ('export const SIZES: Size[] = ["single", "wide", "full"];', 'export const pageTarget', 'versionAtLeast(firmware, "0.2.62") ? MAX_TILES'):
             self.assertIn(marker, layout, marker)
         drawer = editor_sources.component('TileInspector')
-        for marker in ('["full", "Full page"]', 'Goes to page', 'retargetPageTile(tile, Number(v))'):
+        for marker in ('["single", "wide", "full"]', 't("editor.tile.goes_to.label")', 'retargetPageTile(tile, Number(v))'):
             self.assertIn(marker, drawer, marker)
+        self.assertEqual((editor_sources.text('tile.size.full'), editor_sources.text('tile.goes_to.label')), ('Full page', 'Goes to page'))
         self.assertIn(':class="{ wide, full, bare, placeholder: placeholder || !live, chosen }"', editor_sources.component('TileCard'))
-        self.assertIn('["screen", "Screen"]', editor_sources.component('Library'))
+        self.assertIn('"timer", "screen",', editor_sources.component('Library'))
+        self.assertEqual(editor_sources.text('library.filters.screen'), 'Screen')
 
 
 if __name__ == '__main__':