fix: resolve dotnet publish --no-restore issues with multi-architecture builds

- Add BUILDPLATFORM and TARGETARCH support to Dockerfile
- Use architecture-specific restore and publish commands
- Remove problematic --no-restore flag to prevent NuGet resolution errors
- Supports both ARM64 and x86_64 builds
- Resolves build issues reported in PayrollEngine/PayrollEngine#2

Author: gsayer

Dockerfile

@@ -1,4 +1,7 @@
-FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
+# Build stage with multi-platform support
+FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:9.0 AS build
+ARG TARGETARCH
+ARG BUILDPLATFORM
 WORKDIR /src
 
 # copy solution and project files
@@ -12,15 +15,26 @@ COPY ["ViewModel/PayrollEngine.WebApp.ViewModel.csproj", "ViewModel/"]
 # copy Directory.Build.props
 COPY ["Directory.Build.props", "./"]
 
-RUN dotnet restore "PayrollEngine.WebApp.sln"
+# Restore with architecture-specific runtime
+RUN if [ "$TARGETARCH" = "arm64" ]; then \
+      dotnet restore "PayrollEngine.WebApp.sln" --runtime linux-arm64; \
+    else \
+      dotnet restore "PayrollEngine.WebApp.sln" --runtime linux-x64; \
+    fi
 
 # copy everything else
 COPY . .
 WORKDIR "/src/Server"
-RUN dotnet publish "PayrollEngine.WebApp.Server.csproj" -c Release -o /app/publish --no-restore
+
+# Publish with architecture-specific runtime and restore included
+RUN if [ "$TARGETARCH" = "arm64" ]; then \
+      dotnet publish "PayrollEngine.WebApp.Server.csproj" -c Release -o /app/publish --runtime linux-arm64 --self-contained false; \
+    else \
+      dotnet publish "PayrollEngine.WebApp.Server.csproj" -c Release -o /app/publish --runtime linux-x64 --self-contained false; \
+    fi
 
 # final stage
 FROM mcr.microsoft.com/dotnet/aspnet:9.0
 WORKDIR /app
 COPY --from=build /app/publish .
-ENTRYPOINT ["dotnet", "PayrollEngine.WebApp.Server.dll"] 
+ENTRYPOINT ["dotnet", "PayrollEngine.WebApp.Server.dll"]