fix: stop infinite loading spinner when user has no company

Dashboard pages hung on "加载仪表盘数据..." when auth.company was null
(e.g. admin user). Now sets loading=false immediately when no company
is present, so the page renders instead of spinning forever.

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/purchaser/Dashboard.tsx

@@ -74,7 +74,10 @@ export function PurchaserDashboard() {
   }, []);
 
   useEffect(() => {
-    if (!auth.company) return;
+    if (!auth.company) {
+      setLoading(false);
+      return;
+    }
     // 如果数据已加载，不再重新加载
     if (dataLoaded && plans.length > 0) {
       setLoading(false);

src/pages/textile/Dashboard.tsx

@@ -62,7 +62,10 @@ export function TextileDashboard() {
   }, []);
 
   useEffect(() => {
-    if (!auth.company) return;
+    if (!auth.company) {
+      setLoading(false);
+      return;
+    }
     fetchPlans();
     // 从 localStorage 读取被拒绝的计划ID
     const stored = localStorage.getItem(STORAGE_KEYS.textileRejectedPlans);

src/pages/washing/Dashboard.tsx

@@ -69,7 +69,10 @@ export function WashingDashboard() {
   }, []);
 
   useEffect(() => {
-    if (!auth.company) return;
+    if (!auth.company) {
+      setLoading(false);
+      return;
+    }
     fetchPlans();
   }, [auth.company]);