feat(app,viewer): WeChat card share + 'Share to...' label + site og tags

- 按钮文字「分享到微信/其他应用」→「分享到...」（用户需求）
- 微信卡片分享（fluwx 6）：WECHAT_APPID 经 --dart-define 注入；已配置且
  装微信 → WXWebpage 卡片（标题=相册名、描述=日期·地点、缩略图=封面压缩
  240px PNG ≤32KB、点击进观众链接）；未配置/未装 → 回退系统分享面板
- viewer index.html 加站点级 og 标签（微信/QQ 抓取链接预览用；每相册动态
  og 需服务端注入，登记后续增强）
- 397/397 全绿、analyze 0

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

apps/viewer/e2e/embed-v2.spec.ts

@@ -321,11 +321,24 @@ test.describe.serial('E04 interactions: pause, click lock, keyboard, destroy', (
     const target = inside.locator('a.stream-photo').first();
     const photoId = await target.getAttribute('data-photo-id');
     expect(photoId).toBeTruthy();
-    const popupPromise = page.waitForEvent('popup', { timeout: 5000 });
+    // 宿主内弹框（用户决策 2026-09-23）：不新开标签，宿主页覆盖层 + 详情 iframe。
+    let popupOpened = false;
+    page.once('popup', () => {
+      popupOpened = true;
+    });
     await target.click();
-    const popup = await popupPromise;
-    expect(popup.url()).toContain(`/p/${photoId}`);
-    await popup.close();
+    const modalFrame = page.locator('iframe[title="PhotoLive photo detail"]');
+    await modalFrame.waitFor({ timeout: 5000 });
+    expect(popupOpened).toBe(false);
+    await expect
+      .poll(async () => {
+        const f = page.frames().find((fr) => (fr.url().includes('/p/') ?? false));
+        return f?.url() ?? '';
+      })
+      .toContain(`/p/${photoId}`);
+    await page.screenshot({ path: `${OUT_ROOT}/actual/server/photo-modal.png` });
+    await page.keyboard.press('Escape');
+    await expect(modalFrame).toHaveCount(0);
   });
 
   test('drag beyond 8px cancels click (§4.1)', async ({ page }) => {