feat(earth): toolbar and zoom improvements

- Add box-sizing/padding normalization to toolbar buttons
- Remove zoom slider, implement click/hold zoom behavior (+/- buttons)
- Add 10% step on click, 1% continuous on hold
- Fix satellite init: show satellite points immediately, delay trail visibility
- Fix breathing effect: faster pulse, wider opacity range
- Add toggle-cables functionality with visibility state
- Initialize satellites and cables as visible by default

frontend/public/earth/js/satellites.js

@@ -7,8 +7,9 @@ import { CONFIG, SATELLITE_CONFIG } from './constants.js';
 let satellitePoints = null;
 let satelliteTrails = null;
 let satelliteData = [];
-let showSatellites = false;
+let showSatellites = true;
 let showTrails = true;
+let trailsReady = false;
 let animationTime = 0;
 let selectedSatellite = null;
 let satellitePositions = [];
@@ -320,6 +321,10 @@ export function updateSatellitePositions(deltaTime = 0) {
   
   satelliteTrails.geometry.attributes.position.needsUpdate = true;
   satelliteTrails.geometry.attributes.color.needsUpdate = true;
+  
+  if (!trailsReady && count > 0 && satellitePositions[0]?.trail.length >= TRAIL_LENGTH) {
+    trailsReady = true;
+  }
 }
 
 export function toggleSatellites(visible) {
@@ -328,14 +333,14 @@ export function toggleSatellites(visible) {
     satellitePoints.visible = visible;
   }
   if (satelliteTrails) {
-    satelliteTrails.visible = visible && showTrails;
+    satelliteTrails.visible = visible && showTrails && trailsReady;
   }
 }
 
 export function toggleTrails(visible) {
   showTrails = visible;
   if (satelliteTrails) {
-    satelliteTrails.visible = visible && showSatellites;
+    satelliteTrails.visible = visible && showSatellites && trailsReady;
   }
 }