sw.js uses __BUILDVER__ token; build.ps1 replaces it with the git
version before go build (which embeds the patched file), then restores
the template via the finally block. Installed PWA clients receive new
assets after every release.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Add build.ps1: one-shot PowerShell build with version from git tag
- winamp_path config is now optional; roadamp works with any running
  Winamp instance regardless of install location (FindWindow does the
  discovery). Path is only needed if roadamp should launch Winamp itself.
- Remove hardcoded C:\Program Files\Winamp default

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>