Add loading indicators for city detail sync

frontend/components/dashboard/Dashboard.module.css

@@ -606,6 +606,30 @@
   margin-bottom: 6px;
 }
 
+.root :global(.panel-loading-hint) {
+  display: inline-flex;
+  align-items: center;
+  gap: 8px;
+  margin-bottom: 10px;
+  padding: 6px 10px;
+  border-radius: 999px;
+  border: 1px solid rgba(34, 211, 238, 0.18);
+  background: rgba(12, 24, 42, 0.78);
+  color: var(--accent-cyan);
+  font-size: 11px;
+  font-weight: 600;
+  letter-spacing: 0.2px;
+}
+
+.root :global(.panel-loading-spinner) {
+  width: 10px;
+  height: 10px;
+  border-radius: 999px;
+  border: 2px solid rgba(34, 211, 238, 0.22);
+  border-top-color: rgba(34, 211, 238, 0.92);
+  animation: loading-spin 0.8s linear infinite;
+}
+
 .root :global(.panel-meta) {
   display: flex;
   align-items: center;
@@ -613,6 +637,46 @@
   flex-wrap: wrap;
 }
 
+.root :global(.city-loading-toast) {
+  position: fixed;
+  top: 78px;
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 1200;
+  display: inline-flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 14px;
+  border-radius: 999px;
+  border: 1px solid rgba(34, 211, 238, 0.18);
+  background: linear-gradient(
+    180deg,
+    rgba(10, 18, 34, 0.94),
+    rgba(10, 18, 34, 0.82)
+  );
+  box-shadow:
+    0 18px 40px rgba(2, 6, 23, 0.38),
+    0 0 0 1px rgba(34, 211, 238, 0.04) inset;
+  backdrop-filter: blur(18px);
+  pointer-events: none;
+}
+
+.root :global(.city-loading-dot) {
+  width: 10px;
+  height: 10px;
+  border-radius: 999px;
+  background: var(--accent-cyan);
+  box-shadow: 0 0 0 0 rgba(34, 211, 238, 0.5);
+  animation: city-loading-pulse 1.35s ease-out infinite;
+}
+
+.root :global(.city-loading-copy) {
+  color: var(--text-primary);
+  font-size: 12px;
+  font-weight: 600;
+  letter-spacing: 0.25px;
+}
+
 .root :global(.pro-locked) {
   filter: grayscale(0.8) opacity(0.7);
   position: relative;
@@ -1596,6 +1660,21 @@
   }
 }
 
+@keyframes city-loading-pulse {
+  0% {
+    transform: scale(0.92);
+    box-shadow: 0 0 0 0 rgba(34, 211, 238, 0.44);
+  }
+  70% {
+    transform: scale(1);
+    box-shadow: 0 0 0 10px rgba(34, 211, 238, 0);
+  }
+  100% {
+    transform: scale(0.92);
+    box-shadow: 0 0 0 0 rgba(34, 211, 238, 0);
+  }
+}
+
 @keyframes radar-sweep {
   from {
     transform: rotate(0deg);

frontend/components/dashboard/DetailPanel.tsx

@@ -317,6 +317,16 @@ export function DetailPanel() {
         </button>
         <div className="panel-title-area">
           <h2>{panelDisplayName.toUpperCase()}</h2>
+          {store.loadingState.cityDetail && (
+            <div className="panel-loading-hint" role="status" aria-live="polite">
+              <span className="panel-loading-spinner" aria-hidden="true" />
+              <span>
+                {locale === "en-US"
+                  ? `Syncing ${panelDisplayName}...`
+                  : `正在同步 ${panelDisplayName}...`}
+              </span>
+            </div>
+          )}
           <div className="panel-meta">
             <span className={clsx("risk-badge", panelRiskLevel)}>
               {getRiskBadgeLabel(panelRiskLevel, locale)}

frontend/components/dashboard/PolyWeatherDashboard.tsx

@@ -45,6 +45,11 @@ const FutureForecastModal = dynamic(
 function DashboardScreen() {
   const store = useDashboardStore();
   const { t } = useI18n();
+  const activeCityName =
+    store.selectedDetail?.display_name ||
+    store.cities.find((city) => city.name === store.selectedCity)?.display_name ||
+    store.selectedCity ||
+    "";
 
   useEffect(() => {
     const onKeyDown = (event: KeyboardEvent) => {
@@ -79,6 +84,14 @@ function DashboardScreen() {
       <HeaderBar />
       <CitySidebar />
       <DetailPanel />
+      {store.loadingState.cityDetail && activeCityName ? (
+        <div className="city-loading-toast" role="status" aria-live="polite">
+          <span className="city-loading-dot" aria-hidden="true" />
+          <span className="city-loading-copy">
+            {t("dashboard.loading")} {activeCityName}
+          </span>
+        </div>
+      ) : null}
       {store.historyState.isOpen && <HistoryModal />}
       {store.futureModalDate && <FutureForecastModal />}
       {showLoading && (