Update GitHub Actions to latest versions

- Updated actions/checkout from v4 to v5
- Updated actions/setup-dotnet from v4 to v5
- Quoted dotnet-version for better YAML compatibility
- Ensures compatibility with .NET 10 (released November 11, 2025)

Author: claude

.github/workflows/dotnet.yml

@@ -12,11 +12,11 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
     - name: Setup .NET
-      uses: actions/setup-dotnet@v4
+      uses: actions/setup-dotnet@v5
       with:
-        dotnet-version: 10.0.x
+        dotnet-version: '10.0.x'
 
     - name: Check Tag
       id: check-tag