桌面端下载器重构为工作台布局，并重做在线看阅读器

- 左侧导航轨 + 主视图 + 常驻详情检查器，替换原左右两栏平铺卡片结构
- 拆分为 TaskView / TaskRow / SearchView / SettingsView / DetailPanel /
  NavRail / AuthScreen，删除 DashBoard、Side、HentaiSearch
- 在线看改为全屏阅读器：适应高度/宽度、常驻翻页栏、缩略图与标题信息，
  翻页改为状态驱动，不再点击内部 DOM；补键盘快捷键与大图查看
- 提交弹层默认选中原图（无原图时选体积最大的一个）
- 管理员可见「下载人」筛选与详情里的下载人昵称，判定改用后端 isAdmin
- store.deleteGallery 返回 promise，便于删除后清理选中态
- 新增 thumbnail 工具与 4 项单测

tests/thumbnail.test.mjs

@@ -0,0 +1,33 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import {pickDefaultResolution, ehThumbnailUrl} from '../src/utils/thumbnail.js'
+
+test('original resolution wins whenever it is offered', () => {
+    assert.equal(pickDefaultResolution({
+        '800x': '37.53MiB',
+        '1280x': '66.57MiB',
+        '2560x': '84.01MiB',
+        'Original': '498.2MiB'
+    }), 'Original')
+})
+
+test('without an original entry the largest file is chosen', () => {
+    // 1920x is bigger than 2560x here, so byte size decides, not the label.
+    assert.equal(pickDefaultResolution({
+        '800x': '37.53MiB',
+        '1920x': '811.1MiB',
+        '2560x': '84.01MiB'
+    }), '1920x')
+})
+
+test('an empty or missing resolution map yields an empty choice', () => {
+    assert.equal(pickDefaultResolution({}), '')
+    assert.equal(pickDefaultResolution(undefined), '')
+})
+
+test('thumbnail urls carry the path and the active auth code', () => {
+    const url = new URL(ehThumbnailUrl('https://example.org/t?a=1&b=2', 'code with spaces'))
+    assert.equal(url.searchParams.get('path'), 'https://example.org/t?a=1&b=2')
+    assert.equal(url.searchParams.get('AuthCode'), 'code with spaces')
+    assert.equal(ehThumbnailUrl('', 'x'), '')
+})