refactor: remove unused autoprefixer and postcss dependencies from web package

[jongio]

Summary

The web docs site (Tailwind v4.3 + @tailwindcss/vite) still lists autoprefixer and postcss as devDependencies in web/package.json. Neither package is imported or configured anywhere in the project.

Tailwind CSS v4 handles autoprefixing and PostCSS processing internally through its Vite plugin (@tailwindcss/vite), making these explicit dependencies unnecessary.

Current State

"devDependencies": {
  "autoprefixer": "^10.4.24",
  "postcss": "^8.5.6",
  ...
}

No postcss.config.* file exists, and neither package is imported in any source file.

Recommended Fix

Remove both packages from web/package.json devDependencies and run pnpm install to update the lockfile.

Impact

• Reduces dependency surface area and install size
• Eliminates potential version conflicts with Tailwind v4 internals
• Aligns with Tailwind v4 migration guide recommendations