fix: polish earth toolbar controls and loading copy

frontend/public/earth/js/controls.js

@@ -371,7 +371,7 @@ function updateRotateUI() {
   const btn = document.getElementById("rotate-toggle");
   if (btn) {
     btn.classList.toggle("active", autoRotate);
-    btn.innerHTML = autoRotate ? "⏸️" : "▶️";
+    btn.classList.toggle("is-stopped", !autoRotate);
     const tooltip = btn.querySelector(".tooltip");
     if (tooltip) tooltip.textContent = autoRotate ? "暂停旋转" : "开始旋转";
   }

frontend/public/earth/js/main.js

@@ -9,6 +9,7 @@ import {
   updateZoomDisplay,
   updateEarthStats,
   setLoading,
+  setLoadingMessage,
   showTooltip,
   hideTooltip,
   showError,
@@ -392,6 +393,12 @@ async function loadData(showWhiteSphere = false) {
   const loadToken = ++currentLoadToken;
   isDataLoading = true;
   hideError();
+  setLoadingMessage(
+    showWhiteSphere ? "正在刷新全球态势数据..." : "正在初始化全球态势数据...",
+    showWhiteSphere
+      ? "重新同步卫星、海底光缆与登陆点数据"
+      : "同步卫星、海底光缆与登陆点数据",
+  );
   setLoading(true);
   clearLockedObject();
   hideInfoCard();
@@ -761,11 +768,19 @@ function animate() {
 
   const earth = getEarth();
   const deltaTime = clock.getDelta() * 1000;
+  const hasInertia =
+    Math.abs(inertialVelocity.x) > INERTIA_MIN_VELOCITY ||
+    Math.abs(inertialVelocity.y) > INERTIA_MIN_VELOCITY;
 
   if (getAutoRotate() && earth) {
     earth.rotation.y += CONFIG.rotationSpeed * (deltaTime / 16);
-    targetRotation.y = earth.rotation.y;
-    targetRotation.x = earth.rotation.x;
+
+    // Keep the drag target aligned with autorotation only when the user is not
+    // actively dragging and there is no residual inertial motion to preserve.
+    if (!isDragging && !hasInertia) {
+      targetRotation.y = earth.rotation.y;
+      targetRotation.x = earth.rotation.x;
+    }
   }
 
   if (earth) {

frontend/public/earth/js/ui.js

@@ -73,6 +73,19 @@ export function setLoading(loading) {
   loadingEl.style.display = loading ? "block" : "none";
 }
 
+export function setLoadingMessage(title, subtitle = "") {
+  const titleEl = document.getElementById("loading-title");
+  const subtitleEl = document.getElementById("loading-subtitle");
+
+  if (titleEl) {
+    titleEl.textContent = title;
+  }
+
+  if (subtitleEl) {
+    subtitleEl.textContent = subtitle;
+  }
+}
+
 // Show tooltip
 export function showTooltip(x, y, content) {
   const tooltip = document.getElementById("tooltip");