fix: refine earth hud structure and bun startup flow

- refactor the /earth HUD into class-first CSS layers with dedicated base, hud, and toolbar responsibilities
- clean up Earth markup and runtime DOM hooks so shared panel, toolbar, tooltip, and status classes stay consistent after dynamic updates
- keep HUD scaling configurable through extracted constants and remove leftover legacy panel/toolbar styling paths
- make planet.sh self-bootstrap Bun and uv by prepending local runtime bins to PATH and auto-installing missing tools in fresh environments
- document Bun as the frontend package manager of record and sync repository version metadata to 0.24.1

frontend/public/earth/js/constants.js

@@ -12,6 +12,13 @@ export const CONFIG = {
   dragRotationScaleMax: 2.0,
 };
 
+export const HUD_CONFIG = {
+  scaleReferenceWidth: 1920,
+  scaleReferenceHeight: 1080,
+  minScale: 0.7,
+  maxScale: 1,
+};
+
 // Earth coordinate constants
 export const EARTH_CONFIG = {
   tilt: 23.5,  // earth tilt angle (degrees)