Support full trim publishing

[Marc-André Moreau (mamoreau-devolutions)]

Summary

• Switch the Avalonia app default publish mode from TrimMode=partial to TrimMode=full while keeping self-contained ReadyToRun publishing.
• Replace Octokit usage with a narrow, trim-safe GitHubApiClient using HttpClient and source-generated System.Text.Json DTOs for OAuth, device flow, current user, and gist backup APIs.
• Statically root the conditional Windows Mica styles as a typed ResourceDictionary; the first full-trim launch exposed this because the dynamically loaded Styles.WindowsMica.axaml resource was trimmed.
• Add targeted handling for app-owned trim warnings: AUMID shortcut COM activation suppression, expected Avalonia constructor warning suppression, and non-blocking CI visibility for full-trim publish warnings.

Size impact

Measured against same-code x64 Release self-contained ReadyToRun publishes:

Build	Raw publish	Zipped publish
Partial trim	135.01 MiB	59.21 MiB
Full trim	115.62 MiB	50.31 MiB
Savings	19.39 MiB / 14.4%	8.90 MiB / 15.0%

Earlier installer measurement showed a similar gain: 44.56 MiB -> 36.66 MiB, about 7.9 MiB smaller.

Full-trim warning audit

Full-trim publish succeeds and now leaves 45 trim warnings, all from external dependencies:

Category	Count	Notes
Avalonia DataGrid/Controls	10	Reflection/converter paths in Avalonia DataGrid. UniGetUI uses explicit template columns with AutoGenerateColumns="False", but grids still need careful manual validation.
WinRT ABI generated code	35	CsWinRT/WinRT ABI generic annotation warnings from Windows package manager interop. Review WinGet/native package-manager paths carefully.
Octokit/AppShortcut/Mica/AVLN3001	0	App-owned warning categories cleared.

I intentionally did not blanket-suppress the remaining external warnings so future app-owned trim regressions stay visible.

Needs careful review

• Package list DataGrid behavior: installed packages, updates, search/discover, sorting, selection, context menus, details dialogs.
• Desktop shortcut manager DataGrid behavior.
• WinGet / Windows Package Manager COM interop paths, including manager initialization and package queries.
• GitHub auth and backup flows using the new API client: loopback OAuth, device flow IPC auth, avatar/current-user loading, gist create/list/get/update, backup upload/download/restore.
• Windows-specific shell paths: AUMID shortcut stamping, toast notifications, tray restore/quit behavior, and Mica/acrylic styling.

Validation

• dotnet restore src/UniGetUI.Windows.slnx
• dotnet build src/UniGetUI.Windows.slnx --no-restore --verbosity q --nologo /p:Platform=x64 /p:UseSharedCompilation=false /m:1
• dotnet test src/UniGetUI.Windows.slnx --no-restore --verbosity q --nologo /p:Platform=x64 /p:UseSharedCompilation=false /m:1
• dotnet format whitespace src --folder --verify-no-changes --verbosity minimal
• dotnet format style src/UniGetUI.Windows.slnx --no-restore --verify-no-changes --verbosity minimal
• Full-trim x64 Release publish with TrimmerSingleWarn=false
• Launched the full-trim published UniGetUI.exe successfully and inspected the backup settings UI path