Avalonia12 (#7)

* ava12升级

* Enable centralized package versioning

Add <Project> and <PropertyGroup> with <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally> to Directory.Packages.props to enable centralized package version management across the repository. This allows package versions to be controlled from this single file instead of individual project files.

* Migrate codebase to Avalonia 12 APIs

Apply Avalonia 12 migration changes: replace SystemDecorations with WindowDecorations and remove ExtendClientAreaChromeHints/ExtendClientAreaTitleBarHeightHint usages; update BindingPlugins removal logic (no-op); switch clipboard usage to ClipboardExtensions.SetTextAsync; update Bitmap.CopyPixels calls to the new signature. Replace TextBox.Watermark with PlaceholderText, convert NumberBox styles to FANumberBox and adjust templates, change Checked/Unchecked handlers to IsCheckedChanged, and adapt FluentIcons usages (SymbolIconSource -> FASymbol/FAFont/FluentIcon equivalents). Fix MainWindow partial classes to inherit Window and correct missing variables/fields/usings. Add migration docs/specs/tasks under .trae and include a small TestFluentIcons project for icon testing.

* Migrate to Avalonia 12 and Plugin SDK v5

Upgrade project to the Avalonia 12 baseline and Plugin SDK v5: centralize Avalonia packages, remove legacy WebView.Avalonia usage (use NativeWebView/WebView2 EnvironmentRequested), and update Fluent/Material icon/package usages. Bump multiple package/project versions to 5.0.0 and Avalonia 12.0.1, update plugin template and README/docs to SDK v5, and add PLUGIN_SDK_V5_MIGRATION.md.

Also fix runtime/behavior bugs: make DataLocationResolver use a fixed bootstrap launcher data path and avoid recursive ResolveDataRoot; add legacy-state handling and extraction in OobeStateService; and update component settings tests to reflect migrated storage (DB/backup) and reset cache for test reloads. Various csproj, tests, and docs updated to reflect the migration and ensure build/test compatibility.

* Update icon glyphs and symbol mappings

Replace and refine icon sources across settings pages and controls: many FAFontIconSource glyphs were updated to specific Seagull Fluent Icons codepoints, some FASymbolIconSource usages were replaced with FAFontIconSource, and a number of symbol-to-Symbol enum mappings were adjusted (e.g. "Bell" -> AlertOn, "Shield" -> ShieldLock). Also clarified a comment in SettingsWindow and fixed a trailing newline in StudySettingsPage. Changes standardize icon visuals and bridge FluentIcons glyphs into FluentAvalonia icon sources.

* fix.修复合并产生的问题。

.trae/specs/avalonia-12-migration/checklist.md

@@ -0,0 +1,21 @@
+# Checklist
+
+- [x] `Directory.Packages.props` contains the Avalonia 12 dependency baseline.
+- [x] Main host references `Avalonia.Controls.WebView`.
+- [x] Source no longer references `WebView.Avalonia`, `AvaloniaWebView`, or `.UseDesktopWebView()`.
+- [x] `BrowserWidget` uses `NativeWebView.Source`, `Navigate`, `Refresh()`, `NavigationStarted`, and `EnvironmentRequested`.
+- [x] WebView blanking navigates to `about:blank`.
+- [x] Plugin SDK package version is `5.0.0`.
+- [x] `PluginSdkInfo.ApiVersion` is `5.0.0`.
+- [x] Plugin template package version default is `5.0.0`.
+- [x] Plugin template manifest `apiVersion` is `5.0.0`.
+- [x] Launcher data location config resolution cannot recurse through `ResolveDataRoot()`.
+- [x] `OobeStateServiceTests` pass.
+- [x] `dotnet build LanMountainDesktop.slnx -c Debug` has 0 errors.
+- [x] `dotnet test LanMountainDesktop.slnx -c Debug` completes without a test host stack overflow.
+- [ ] Windows host smoke test completed.
+- [ ] Windows Launcher smoke test completed.
+- [ ] Settings window FluentAvalonia 3 smoke test completed.
+- [ ] Component editor Material smoke test completed.
+- [ ] BrowserWidget navigation/refresh/page activation smoke test completed.
+- [ ] WebView2 missing-runtime diagnostic smoke test completed.