Fix build-container publish failure by installing Tailwind CLI from npm

[Copilot]

The build-container workflow was failing during dotnet publish because MyApp's postinstall.js fell back to downloading the standalone Tailwind binary from GitHub, and that network-dependent path failed in Actions. This change makes the Tailwind CLI available through npm so publish no longer depends on that external binary download.

• Root cause

  • MyApp/package.json did not provide a local tailwindcss CLI.
  • During npm install, postinstall.js attempted to fetch the latest standalone Tailwind binary from GitHub and aborted when that download failed.

• Change

  • Added npm-managed dev dependencies in MyApp/package.json:
    • @tailwindcss/cli
    • tailwindcss

• Effect on publish/build flow

  • tailwindcss is now present in PATH during npm install.
  • postinstall.js detects the CLI and skips the remote binary download path.
  • Existing ui:build and publish behavior remain unchanged.

{
  "devDependencies": {
    "@tailwindcss/cli": "^4.1.18",
    "tailwindcss": "^4.1.18"
  }
}