feat(scripts): extend nomarchy-welcome into a guided wizard

- Added nomarchy.panelPosition option and state persistence.
- Updated Waybar to respect the panelPosition setting.
- Refactored nomarchy-welcome to use state.json instead of a flag file.
- Added prompts for theme, font, panel position, and starter home.nix generation.
- Updated documentation and roadmap.

lib/state-schema.nix

@@ -9,6 +9,7 @@
     theme = "nord";
     wallpaper = "";
     font = "JetBrainsMono Nerd Font";
+    panelPosition = "top";
     nightlightTemperature = 4000;
 
     # Feature toggles