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/pages/Activity.tsx

@@ -0,0 +1,49 @@
+import { useCallback } from "react";
+import { activityApi } from "../api/activity";
+import { useCompany } from "../context/CompanyContext";
+import { useApi } from "../hooks/useApi";
+import { formatDate } from "../lib/utils";
+import { Card, CardContent } from "@/components/ui/card";
+
+export function Activity() {
+  const { selectedCompanyId } = useCompany();
+
+  const fetcher = useCallback(() => {
+    if (!selectedCompanyId) return Promise.resolve([]);
+    return activityApi.list(selectedCompanyId);
+  }, [selectedCompanyId]);
+
+  const { data, loading, error } = useApi(fetcher);
+
+  if (!selectedCompanyId) {
+    return <p className="text-muted-foreground">Select a company first.</p>;
+  }
+
+  return (
+    <div>
+      <h2 className="text-2xl font-bold mb-4">Activity</h2>
+      {loading && <p className="text-muted-foreground">Loading...</p>}
+      {error && <p className="text-destructive">{error.message}</p>}
+
+      {data && data.length === 0 && <p className="text-muted-foreground">No activity yet.</p>}
+
+      {data && data.length > 0 && (
+        <div className="space-y-2">
+          {data.map((event) => (
+            <Card key={event.id}>
+              <CardContent className="p-3 text-sm">
+                <div className="flex items-center justify-between gap-2">
+                  <span className="font-medium">{event.action}</span>
+                  <span className="text-xs text-muted-foreground">{formatDate(event.createdAt)}</span>
+                </div>
+                <p className="text-xs text-muted-foreground mt-1">
+                  {event.entityType} {event.entityId}
+                </p>
+              </CardContent>
+            </Card>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}