Migrate Tailwind v4 config

[peterpeterparker]

The templates were migrated to Tailwind v4 in #70, but they still rely on tailwind.config.js|mjs|ts instead of adopting the new theming approach.

For example:

@theme {
  --color-*: initial;
  --color-inherit: inherit;
  --color-transparent: transparent;
  --color-current: currentColor;
  --color-black: rgb(0 0 0);
  --color-white: rgb(255 255 255);

  --color-lavender-blue-50: #f2f3ff;
  --color-lavender-blue-100: #e4e7ff;
  --color-lavender-blue-200: #c9cfff;
  --color-lavender-blue-300: #aeb8ff;
  --color-lavender-blue-400: #93a0ff;
  --color-lavender-blue-500: #7888ff;
  --color-lavender-blue-600: #606dcc;
  --color-lavender-blue-700: #485299;
  --color-lavender-blue-800: #303666;
  --color-lavender-blue-900: #181b33;
}

Any help with migrating these configurations to the new method would be greatly appreciated.

Resources:

https://tailwindcss.com/blog/tailwindcss-v4

https://tailwindcss.com/docs/upgrade-guide