Support .laapp/plugin.json and improve market models

Add support for the new plugin package contract (.laapp + plugin.json) while keeping backward compatibility with legacy .lmdp/manifest.json, and improve market metadata resolution and launcher handling.

Key changes:
- LanMountainDesktop.Launcher: PluginInstallerService now recognizes plugin.json and .laapp, preserves legacy manifest/package names, searches for manifests with a helper, and removes existing packages matching either extension.
- LanMountainDesktop.PluginTemplate: README updated to document .laapp, plugin.json, runtime contract and packaging expectations.
- Tests: New and extended tests for PluginInstallerService and a PluginMarketIndexDocumentTests covering nested index parsing and metadata enrichment.
- LauncherClient & PluginMarketInstallService: ResolveLauncherPath now probes multiple candidate locations (useful for dev and packaged layouts); LauncherClient also adjusted launcher arguments to use the updated CLI form.
- SettingsDomainServices: Added BuildCapabilities to safely build capability lists from entries (null checks, projection, de-dup via DistinctBy).
- AirAppMarketMetadataResolverService & PluginMarketModels: Prefer existing manifest/publication/compatibility values when enriching entries, add ApiVersion/Path fields, normalize compatibility logic and package source URL/path handling; handle Sha256/size/publication dates more robustly.
- Misc: Added localization spec/checklist/tasks under .trae for a localization fix initiative.

These changes enable the new plugin packaging format, improve robustness of market data enrichment, make launcher discovery more flexible for different environments, and add tests and docs to cover the new behaviors.

.trae/specs/localization-fix/checklist.md

@@ -0,0 +1,42 @@
+# 本地化修复 Checklist
+
+## MainWindow 修复
+- [ ] `TaskbarProfileDisplayNameTextBlock.Text` 在中文下显示"用户"（或保持动态）
+- [ ] `TaskbarProfileSettingsActionTextBlock.Text` 在中文下显示"设置"
+- [ ] `TaskbarProfileDesktopEditActionTextBlock.Text` 在中文下显示"桌面编辑"
+- [ ] `TaskbarProfilePowerActionTextBlock.Text` 在中文下显示"电源"
+- [ ] `TaskbarPowerBackTextBlock.Text` 在中文下显示"返回"
+- [ ] `TaskbarPowerTitleTextBlock.Text` 在中文下显示"电源"
+- [ ] `PowerShutdownTextBlock.Text` 在中文下显示"关机"
+- [ ] `PowerRestartTextBlock.Text` 在中文下显示"重启"
+- [ ] `PowerLogoutTextBlock.Text` 在中文下显示"注销"
+- [ ] `PowerSleepTextBlock.Text` 在中文下显示"睡眠"
+- [ ] `PowerLockTextBlock.Text` 在中文下显示"锁定屏幕"
+- [ ] `ComponentLibraryTitleTextBlock.Text` 在中文下显示"桌面编辑"
+- [ ] `ComponentLibraryEmptyTextBlock.Text` 在中文下显示"左右滑动选择类别，点击进入，然后拖动组件到桌面放置。"
+- [ ] `ComponentLibraryBackTextBlock.Text` 在中文下显示"返回"
+- [ ] `ComponentLibraryCollapsedChipTextBlock.Text` 在中文下显示"桌面编辑"
+
+## Launcher 修复
+- [ ] `SplashWindow` 在中文下显示中文启动文本
+- [ ] `DataLocationPromptWindow` 在中文下全部显示中文
+- [ ] `ErrorWindow` 在中文下全部显示中文
+- [ ] `LoadingDetailsWindow` 在中文下全部显示中文
+- [ ] `UpdateWindow` 在中文下显示中文标题
+
+## 组件修复
+- [ ] `BrowserWidget` 在中文下显示"浏览器运行时不可用"
+- [ ] `WhiteboardWidget` 工具提示在中文下显示"笔"、"橡皮擦"、"清空"、"导出 SVG"
+- [ ] `HolidayCalendarWidget` 在中文下显示"节假日倒计时"、"天"
+- [ ] `BilibiliHotSearchWidget` 在中文下显示"热门话题"
+- [ ] `WallpaperSettingsPage` 自定义颜色 Tooltip 在中文下显示"自定义颜色"
+
+## 资源文件
+- [ ] `zh-CN.json` 包含所有新增键值
+- [ ] `en-US.json` 包含所有新增键值
+- [ ] Launcher 本地化文件包含所有新增键值
+
+## 构建与质量
+- [ ] `dotnet build LanMountainDesktop.slnx -c Debug` 编译通过，无错误
+- [ ] 无新增警告
+- [ ] 无遗漏的硬编码英文（通过 `grep -r 'Text="[a-zA-Z]'` 等检查）