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/css/earth-stats.css

@@ -1,51 +1,15 @@
 /* earth-stats */
 
-#earth-stats {
-  bottom: 20px;
-  right: 20px;
-  border-radius: 18px;
-  padding: 15px;
-  width: 250px;
+.hud-panel-stats {
+  bottom: var(--hud-offset);
+  right: var(--hud-offset);
+  border-radius: var(--hud-radius);
+  padding: var(--hud-panel-padding);
+  width: calc(250px * var(--hud-scale));
   z-index: 10;
-  font-size: 0.9rem;
+  font-size: var(--hud-font-size);
 }
 
-#earth-stats .stats-item {
-  margin-bottom: 8px;
-  display: flex;
-  justify-content: space-between;
-}
-
-#earth-stats .stats-label {
-  color: #aaa;
-}
-
-#earth-stats .stats-value {
-  color: #4db8ff;
-  font-weight: 500;
-}
-
-#satellite-info {
-  bottom: 20px;
-  right: 290px;
-  border-radius: 18px;
-  padding: 15px;
-  width: 220px;
-  z-index: 10;
-  font-size: 0.85rem;
-}
-
-#satellite-info .stats-item {
-  margin-bottom: 6px;
-  display: flex;
-  justify-content: space-between;
-}
-
-#satellite-info .stats-label {
-  color: #aaa;
-}
-
-#satellite-info .stats-value {
-  color: #00e5ff;
-  font-weight: 500;
+.hud-panel-stats .stats-item {
+  margin-bottom: var(--hud-gap-sm);
 }