feat(earth): add predicted orbit display for locked satellites

- Calculate orbital period from meanMotion
- Generate predicted orbit points with 10s sampling
- Show complete orbit line when satellite is locked
- Hide orbit when satellite is unlocked
- Color gradient: bright (current) to dark (end)
- Fix TLE epoch format issue with fallback circle orbit
- Add visibility change handler to clear trails on page hide
- Fix satellite count display after loading
- Merge predicted-orbit plan into single file

frontend/public/earth/js/main.js

@@ -14,7 +14,7 @@ import {
 } from './ui.js';
 import { createEarth, createClouds, createTerrain, createStars, createGridLines, toggleTerrain, getEarth } from './earth.js';
 import { loadGeoJSONFromPath, loadLandingPoints, handleCableClick, clearCableSelection, getCableLines, getCablesById, lockedCable as cableLocked, getCableState, setCableState, clearAllCableStates, applyLandingPointVisualState, resetLandingPointVisualState, getAllLandingPoints, getShowCables } from './cables.js';
-import { createSatellites, loadSatellites, updateSatellitePositions, toggleSatellites, toggleTrails, getShowSatellites, selectSatellite, getSatelliteData, getSatellitePoints, setSatelliteRingState, updateLockedRingPosition, updateHoverRingPosition, getSatellitePositions } from './satellites.js';
+import { createSatellites, loadSatellites, updateSatellitePositions, toggleSatellites, toggleTrails, getShowSatellites, getSatelliteCount, selectSatellite, getSatelliteData, getSatellitePoints, setSatelliteRingState, updateLockedRingPosition, updateHoverRingPosition, getSatellitePositions, showPredictedOrbit, hidePredictedOrbit } from './satellites.js';
 import { setupControls, getAutoRotate, getShowTerrain, zoomLevel, setAutoRotate, toggleAutoRotate, resetView } from './controls.js';
 import { initInfoCard, showInfoCard, hideInfoCard, getCurrentType, setInfoCardNoBorder } from './info-card.js';
 
@@ -34,6 +34,7 @@ let dragStartTime = 0;
 let isLongDrag = false;
 
 export function clearLockedObject() {
+  hidePredictedOrbit();
   hoveredCable = null;
   hoveredSatellite = null;
   hoveredSatelliteIndex = null;
@@ -202,6 +203,7 @@ async function loadData(showWhiteSphere = false) {
       (async () => {
         const satCount = await loadSatellites();
         console.log(`卫星数据加载完成: ${satCount} 颗`);
+        document.getElementById('satellite-count').textContent = satCount + ' 颗';
         updateSatellitePositions();
         console.log('卫星位置已更新');
         toggleSatellites(true);
@@ -438,6 +440,7 @@ function onClick(event, camera, renderer) {
       lockedObjectType = 'satellite';
       lockedSatellite = sat;
       lockedSatelliteIndex = index;
+      showPredictedOrbit(sat);
       setAutoRotate(false);
       
       const satPositions = getSatellitePositions();