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/vite.config.ts

@@ -1,9 +1,15 @@
+import path from "path";
 import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 import tailwindcss from "@tailwindcss/vite";
 
 export default defineConfig({
   plugins: [react(), tailwindcss()],
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
   server: {
     port: 5173,
     proxy: {