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

[jfgrissom]

Looking at this today.

Following a process like this might make it relatively painless.

1. Create a new project with a specific template.
2. Modify the project to address the v4 changes.
3. Merge the changes in the project back into the template.
4. Rinse and repeat for each.

Seems like it might be something pretty helpful and I've not played with V4 yet so it could be good to see what has changed.

[jfgrissom]

Here is a PR for the react-starter template.

#85

Happy to handle the others too if this gets merged.