feat(earth): toolbar zoom improvements and toggle-cables

- Remove zoom slider, implement click/hold zoom behavior (+/- buttons)
- Add 10% step on click, 1% continuous on hold
- Add box-sizing/padding normalization to toolbar buttons
- Add toggle-cables functionality with visibility state
- Fix breathing effect: faster pulse (0.008), wider opacity range (0.2-1.0)
- Fix slider null error in updateZoomDisplay
- Set satellite default to hidden

frontend/public/earth/index.html

@@ -38,7 +38,7 @@
 
     <div id="right-toolbar-group">
       <div id="zoom-toolbar">
-        <button id="reset-view" class="zoom-btn">📍</button>
+        <button id="reset-view" class="zoom-btn">🎯</button>
         <button id="zoom-in" class="zoom-btn">+</button>
         <span id="zoom-value" class="zoom-percent">100%</span>
         <button id="zoom-out" class="zoom-btn">−</button>
@@ -49,7 +49,7 @@
           <button id="rotate-toggle" class="toolbar-btn" title="自动旋转">🔄<span class="tooltip">自动旋转</span></button>
           <button id="toggle-cables" class="toolbar-btn active" title="显示/隐藏线缆">🌐<span class="tooltip">隐藏线缆</span></button>
           <button id="toggle-terrain" class="toolbar-btn" title="显示/隐藏地形">⛰️<span class="tooltip">显示/隐藏地形</span></button>
-          <button id="toggle-satellites" class="toolbar-btn active" title="显示/隐藏卫星">🛰️<span class="tooltip">隐藏卫星</span></button>
+          <button id="toggle-satellites" class="toolbar-btn" title="显示/隐藏卫星">🛰️<span class="tooltip">显示卫星</span></button>
           <button id="toggle-trails" class="toolbar-btn" title="显示/隐藏轨迹">✨<span class="tooltip">显示/隐藏轨迹</span></button>
           <button id="reload-data" class="toolbar-btn" title="重新加载数据">🔃<span class="tooltip">重新加载数据</span></button>
         </div>

frontend/public/earth/js/main.js

@@ -201,8 +201,6 @@ async function loadData(showWhiteSphere = false) {
     console.log(`卫星数据加载完成: ${satCount} 颗`);
     updateSatellitePositions();
     console.log('卫星位置已更新');
-    toggleSatellites(true);
-    console.log('卫星已显示');
   } catch (error) {
     console.error('加载数据失败:', error);
     showStatusMessage('加载数据失败: ' + error.message, 'error');

frontend/public/earth/js/satellites.js

@@ -7,9 +7,8 @@ import { CONFIG, SATELLITE_CONFIG } from './constants.js';
 let satellitePoints = null;
 let satelliteTrails = null;
 let satelliteData = [];
-let showSatellites = true;
+let showSatellites = false;
 let showTrails = true;
-let trailsReady = false;
 let animationTime = 0;
 let selectedSatellite = null;
 let satellitePositions = [];
@@ -321,10 +320,6 @@ 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) {
@@ -333,14 +328,14 @@ export function toggleSatellites(visible) {
     satellitePoints.visible = visible;
   }
   if (satelliteTrails) {
-    satelliteTrails.visible = visible && showTrails && trailsReady;
+    satelliteTrails.visible = visible && showTrails;
   }
 }
 
 export function toggleTrails(visible) {
   showTrails = visible;
   if (satelliteTrails) {
-    satelliteTrails.visible = visible && showSatellites && trailsReady;
+    satelliteTrails.visible = visible && showSatellites;
   }
 }