[Feature]: Using Textual for TUI

[oxGorou]

We already built a TUI prototype using Textual back in v0.6.0, but we decided to split the development into two branches: our homemade TUI and another branch that utilized Textual as the main TUI. After two major versions of U4L, we've decided it's time to merge them and officially use Textual as the main TUI starting from v0.9.0. Here is a preview:

[oxGorou]