chore: upgrade GitHub Actions to Node.js 24 compatible versions

- Upgrade actions/checkout from v4 to v7
- Upgrade actions/setup-dotnet from v4 to v5
- Upgrade actions/upload-artifact from v4 to v7
- Upgrade actions/download-artifact from v4 to v4 (already compatible)
- Upgrade ncipollo/release-action from v1 to v1.21.0

This addresses GitHub's deprecation of Node.js 20 and the upcoming
forced migration to Node.js 24 (effective June 2, 2026).

.github/workflows/installer-build.yml

@@ -35,13 +35,13 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
         with:
           fetch-depth: 0
           submodules: recursive
 
       - name: Setup .NET
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.DOTNET_VERSION }}
           dotnet-quality: preview
@@ -129,7 +129,7 @@ jobs:
 
       - name: Upload online installer artifact
         if: matrix.configuration == 'Release'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: LanDesktopPLONDS-online-installer-${{ env.INSTALLER_RUNTIME }}
           path: ${{ env.INSTALLER_ARTIFACT_DIR }}/**