feat(scope): add company scope switcher — two views (by-task all companies / by-company all tasks)

- CompanyScopeContext + Provider with localStorage persistence
- Sidebar company selector (desktop + mobile)
- apiFetch auto-injects company_id on GET requests
- Dashboard summary API supports company_id filter
- Milestones/Financial/DigitalTwins pages use scope instead of manual input
- HealthHeatmap/HealthTrends components react to scope changes

frontend/src/app/(investor)/digital-twins/page.tsx

@@ -3,6 +3,7 @@
 import { useEffect, useState } from "react";
 import {Sparkles } from "lucide-react";
 import { listDigitalTwins, buildDigitalTwin, simulateTwin } from "@/lib/api-v2";
+import { useCompanyScope } from "@/lib/company-scope";
 import { PageContainer, Card, Badge } from "@/components/shared/PageContainer";
 import { LoadingSpinner } from "@/components/shared/LoadingSpinner";
 import { EmptyState } from "@/components/shared/EmptyState";
@@ -20,6 +21,7 @@ interface SimulationResult {
 }
 
 export default function DigitalTwinsPage() {
+  const { companyId } = useCompanyScope();
   const [items, setItems] = useState<DigitalTwinItem[]>([]);
   const [isLoading, setIsLoading] = useState(true);
   const [companyData, setCompanyData] = useState("");
@@ -27,11 +29,17 @@ export default function DigitalTwinsPage() {
   const [simResult, setSimResult] = useState<SimulationResult | null>(null);
 
   useEffect(() => {
-    listDigitalTwins("")
-      .then(() => setItems([]))
+    if (!companyId) {
+      // eslint-disable-next-line react-hooks/set-state-in-effect
+      setItems([]);
+      setIsLoading(false);
+      return;
+    }
+    listDigitalTwins(companyId)
+      .then((resp) => setItems((resp.data as DigitalTwinItem[]) ?? []))
       .catch(() => setItems([]))
       .finally(() => setIsLoading(false));
-  }, []);
+  }, [companyId]);
 
   const handleBuild = async () => {
     if (!companyData.trim()) {
@@ -62,6 +70,10 @@ export default function DigitalTwinsPage() {
 
   return (
     <PageContainer title="数字孪生" description="企业模型 + 场景模拟 + 精度追踪">
+      {!companyId ? (
+        <EmptyState title="请先在侧边栏选择企业" description="数字孪生需要指定具体企业，请在左上角企业选择器中选择" />
+      ) : (
+      <>
       <Card>
         <h3 className="font-medium text-gray-900">构建数字孪生模型</h3>
         <textarea
@@ -124,6 +136,8 @@ export default function DigitalTwinsPage() {
           ))}
         </div>
       )}
+      </>
+      )}
     </PageContainer>
   );
 }