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)/dashboard/page.tsx

@@ -4,6 +4,7 @@ import { useEffect, useState } from "react";
 import { Building2, Heart, AlertTriangle, FileText, TrendingUp, TrendingDown, Minus } from "lucide-react";
 import Link from "next/link";
 import { getDashboardSummary, type DashboardSummary } from "@/lib/dashboard";
+import { useCompanyScope } from "@/lib/company-scope";
 import { LoadingSpinner } from "@/components/shared/LoadingSpinner";
 import { EmptyState } from "@/components/shared/EmptyState";
 import { HealthScoreBadge } from "@/components/shared/HealthScoreBadge";
@@ -13,6 +14,7 @@ import { HealthHeatmap, HealthTrends } from "@/components/dashboard/HealthHeatma
  * 投资人端 — 驾驶舱首页。
  */
 export default function InvestorDashboardPage() {
+  const { companyName } = useCompanyScope();
   const [summary, setSummary] = useState<DashboardSummary | null>(null);
   const [isLoading, setIsLoading] = useState(true);
 
@@ -79,8 +81,8 @@ export default function InvestorDashboardPage() {
   return (
     <div className="space-y-6">
       <div>
-        <h1 className="text-2xl font-bold text-foreground">投资机构驾驶舱</h1>
-        <p className="mt-1 text-sm text-muted-foreground">Portfolio 全局健康度与风险概览</p>
+        <h1 className="text-2xl font-bold text-foreground">{companyName ? `${companyName} — 企业驾驶舱` : "投资机构驾驶舱"}</h1>
+        <p className="mt-1 text-sm text-muted-foreground">{companyName ? "单企业健康度与风险概览" : "Portfolio 全局健康度与风险概览"}</p>
       </div>
 
       {/* KPI 卡片 */}