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/main.tsx

@@ -2,12 +2,15 @@ import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
 import { BrowserRouter } from "react-router-dom";
 import { App } from "./App";
+import { CompanyProvider } from "./context/CompanyContext";
 import "./index.css";
 
 createRoot(document.getElementById("root")!).render(
   <StrictMode>
-    <BrowserRouter>
-      <App />
-    </BrowserRouter>
+    <CompanyProvider>
+      <BrowserRouter>
+        <App />
+      </BrowserRouter>
+    </CompanyProvider>
   </StrictMode>
 );