feat: Add build script to automate setup

[DealsBeam]

This commit introduces a new Windows batch script, build.bat, to fully automate the build process described in BUILDING.md.

The script handles:

• Cloning and bootstrapping vcpkg
• Installing required vcpkg packages
• Building the Chromium Embedded Framework (CEF) from a user-provided directory
• Installing NPM dependencies for the UI
• Creating and installing a test certificate
• Building the main Visual Studio solution

This script significantly simplifies the setup for new and existing developers, reducing the chance of manual errors.

The BUILDING.md file has also been updated to document the usage of this new script.