Theme System
Make color dynamic and shared across surfaces. Evolve bastion-theme::Palette into a surface-agnostic Theme (core colors used by both TUI and the future GUI, plus GUI-only fields — wallpaper, bars, opacity — carried verbatim for later, plus lore metadata). Load themes from ~/Settings/Themes.md (M15 Settings contract): each theme is a ## <Capital> block with an active checkbox and a yaml fence of values; the checked theme is active, none checked falls back to the built-in dpn floor. Pre-supply the user's QML themes (translated from ~/.config/quickshell/theme.json — 19 realm palettes named by capital city + the Dragonpunk dpn/dps/boss built-ins) so the look travels with Bastion to any machine (laptop + Mac Studio). Migrate the duplicated DPN_* chrome consts in main.rs into the Theme. Themes recolor only — the DPN reactor-console aesthetic is invariant.
