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

planet.sh

@@ -25,13 +25,19 @@ start() {
     PYTHONPATH="$SCRIPT_DIR/backend" nohup python3 -m uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload > /tmp/planet_backend.log 2>&1 &
     BACKEND_PID=$!
 
-    sleep 3
-
-    if ! curl -s http://localhost:8000/health > /dev/null 2>&1; then
-        echo -e "${RED}❌ 后端启动失败${NC}"
-        tail -10 /tmp/planet_backend.log
-        exit 1
-    fi
+    echo "    等待后端启动..."
+    for i in {1..10}; do
+        sleep 2
+        if curl -s http://localhost:8000/health > /dev/null 2>&1; then
+            echo -e "    ${GREEN}✅ 后端已就绪${NC}"
+            break
+        fi
+        if [ $i -eq 10 ]; then
+            echo -e "${RED}❌ 后端启动失败${NC}"
+            tail -10 /tmp/planet_backend.log
+            exit 1
+        fi
+    done
 
     echo -e "${BLUE}🌐 启动前端...${NC}"
     pkill -f "vite" 2>/dev/null || true