Overhaul UI with shadcn components and new pages

Add shadcn/ui components (badge, button, card, input, select,
separator). Add company context provider. New pages: Activity,
Approvals, Companies, Costs, Org chart. Restyle existing pages
(Dashboard, Agents, Issues, Goals, Projects) with shadcn components
and dark theme. Update layout, sidebar navigation, and routing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -1,13 +1,43 @@
 import { Outlet } from "react-router-dom";
 import { Sidebar } from "./Sidebar";
+import { useCompany } from "../context/CompanyContext";
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from "@/components/ui/select";
 
 export function Layout() {
+  const { companies, selectedCompanyId, setSelectedCompanyId } = useCompany();
+
   return (
-    <div className="flex h-screen bg-gray-50 text-gray-900">
+    <div className="flex h-screen bg-background text-foreground">
       <Sidebar />
-      <main className="flex-1 overflow-auto p-8">
-        <Outlet />
-      </main>
+      <div className="flex-1 overflow-auto">
+        <header className="bg-card border-b border-border px-8 py-3 flex items-center justify-end">
+          <label className="text-xs text-muted-foreground mr-2">Company</label>
+          <Select
+            value={selectedCompanyId ?? ""}
+            onValueChange={(value) => setSelectedCompanyId(value)}
+          >
+            <SelectTrigger className="w-48 h-8 text-sm">
+              <SelectValue placeholder="No companies" />
+            </SelectTrigger>
+            <SelectContent>
+              {companies.map((company) => (
+                <SelectItem key={company.id} value={company.id}>
+                  {company.name}
+                </SelectItem>
+              ))}
+            </SelectContent>
+          </Select>
+        </header>
+        <main className="p-8">
+          <Outlet />
+        </main>
+      </div>
     </div>
   );
 }