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>

web/tests/store.spec.ts

@@ -1,7 +1,7 @@
 // The store: selecting a screen, editing its layout, what's new, progress, copy and import.
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import {
-  addTile, canAlert, copyLayoutFrom, fullPage, importLayout, layoutJson, liveOf, moveTileToPage, pageReachWarning, pageTilesRepeat, PHASES, removeTile,
+  addTile, canAlert, copyLayoutFrom, fullPage, importLayout, layoutJson, liveOf, moveTileToPage, pageReachWarning, pageTilesRepeat, phaseText, removeTile,
   retargetPageTile, save, select, setTileOption, state, supports, tileLimit, topbarItems, topbarView, updateProgress, whatsNew,
 } from "../src/store";
 import type { Inventory, Screen } from "../src/types";
@@ -141,7 +141,8 @@ describe("updates with content", () => {
     expect(updateProgress(living)).toBeNull();
     living.update!.state = "running";
     living.update!.phase = "install";
-    expect(updateProgress(living)).toEqual({ percent: 12, text: PHASES.install });
+    expect(updateProgress(living)).toEqual({ percent: 12, text: phaseText("install") });
+    expect(phaseText("install")).toBe("Building and installing…");
     state.firmwareJob = { job: { stage: "compile" }, logs: [] };
     expect(updateProgress(living)!.percent).toBe(40);
     state.firmwareJob = { job: { stage: "upload" }, logs: [] };