fix: second build fails with DirectoryNotFoundException (#25)

* refactor: use SVG path icons for theme and locale buttons

- Replace emoji with PathGeometry icons (Sun/Moon/Globe)
- Theme: Moon icon in light mode, Sun icon in dark mode (toggled via IsDarkTheme)
- Locale: Globe icon overlay with EN/中 text label
- Remove ThemeButtonText emoji property from ViewModel

* fix: Config.OutputPath overwritten with .zip path causing second build failure

- After first build, OutputPath was set to the .zip file path
- Second build used it as a directory, creating a broken path
- Fix: don't overwrite OutputPath with .zip, keep it as directory only

Author: JusterZhu

src/ViewModels/PatchViewModel.cs

@@ -55,7 +55,7 @@ [RelayCommand] async Task Build()
             L(_loc.T("Patch.Packing", Path.GetFileName(zip)));
             await _pkg.CompressDirectoryAsync(tmp, zip);
             Directory.Delete(tmp, true);
-            Progress = 100; Config.OutputPath = zip;
+            Progress = 100;
             Status = _loc.T("Patch.Success", Path.GetFileName(zip), new FileInfo(zip).Length / 1024.0);
             L(Status);
         }