Add support for Tailwind CSS class prefix configuration

[ali-shabani]

Problem or use case

When working on projects that require namespaced or prefixed Tailwind CSS classes (e.g., tw-, ui-), there's currently no way to configure UntitledUI to generate components with these prefixes. This is a common requirement for:

Projects integrating multiple design systems
Avoiding class name conflicts with existing CSS
Meeting team/organization styling conventions
Working in micro-frontend architectures

Without this feature, developers must manually add prefixes to all Tailwind classes after component generation, which is time-consuming and error-prone.

Proposed solution

Add a configuration option (similar to shadcn/ui's prefix support) that allows users to specify a Tailwind class prefix. This could be implemented as:

A CLI flag: --prefix="tw-" during installation/add commands
A configuration file option in the UntitledUI config (e.g., tailwind.prefix in the config file)
Automatically detect and use the prefix from tailwind.config.js if one is defined there

When a prefix is configured, all generated components should automatically include it in their className attributes (e.g., className="flex items-center" becomes className="tw-flex tw-items-center").

Alternatives considered

No response

Examples or mockups

No response