Refactor Dockerfile and build script: streamline .NET SDK installation and update run instructions

Dockerfile

@@ -75,8 +75,7 @@ RUN cd /tmp \
     && sleep 3 \
     && wine dotnet-sdk-9.0.301-win-x64.exe /quiet \
     && wineserver --wait \
-    && kill $XVFB_PID || true \
-    && rm dotnet-sdk-9.0.301-win-x64.exe || true
+    && kill $XVFB_PID || true
 
 # Set environment variables for .NET
 ENV DOTNET_ROOT="$WINEPREFIX/drive_c/Program Files/dotnet"
@@ -94,4 +93,4 @@ RUN Xvfb :99 -screen 0 1024x768x16 & \
 WORKDIR /home/wineuser/projects
 
 # Default command
-CMD ["/bin/bash"]
+CMD ["/bin/bash", "-l"]