Initial scaffold: AI Tycoon monorepo with core game loop

Turborepo monorepo with three packages:
- packages/shared: TypeScript types for all 14 game systems + balance constants + formatting utils
- packages/game-engine: Pure TS simulation engine with tick processor, economy, infrastructure, compute, research, market, and reputation systems
- apps/web: React + Vite + Tailwind + Zustand frontend with sidebar dashboard layout, new game screen, dashboard with charts, infrastructure management, and model training pages

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

apps/web/src/index.css

@@ -0,0 +1,25 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+  * {
+    @apply border-surface-700;
+  }
+
+  ::-webkit-scrollbar {
+    @apply w-2;
+  }
+
+  ::-webkit-scrollbar-track {
+    @apply bg-surface-900;
+  }
+
+  ::-webkit-scrollbar-thumb {
+    @apply bg-surface-600 rounded-full;
+  }
+
+  ::-webkit-scrollbar-thumb:hover {
+    @apply bg-surface-500;
+  }
+}