Feature: Add support for custom color theming

[luckawalkerr]

Is your feature request related to a problem?

When using impala in a terminal with a dark theme (like Vantablack with #0d0d0d background), the default highlight/selection colors have very poor contrast and are nearly unreadable. Since impala uses ratatui/crossterm with hardcoded RGB colors, it ignores the terminal's ANSI color palette entirely.

Describe the solution you'd like

Add a [style] or [theme] section in config.toml to customize colors, similar to how other TUI apps handle theming. For example:

[style]
selected_fg = "#ffffff"
selected_bg = "#3a3a3a"
header_fg = "#ffffff"
border = "#8d8d8d"

Or at minimum, support for respecting the terminal's ANSI color palette for highlighted/selected items.

Additional context

• impala version: 0.7.4
• Terminal: Alacritty on Hyprland (Wayland)
• Related: pythops/bluetui has the same issue (see issue Censor password by default and add a toggle option for showing password #29)

Thanks for the great tool!

[unatried]

You mean pythops/bluetui#29.

I think since @pythops is using a similar TUI "framework" for all of his TUI applications, if he implements it in either, it will, or at least be easier to implement in other TUIs.