feat: scaffold Tauri v2 + React + TS with all dependencies

- Tauri v2 with React 19 + TypeScript + Vite 7
- Tauri plugins: fs, dialog, shell (registered in lib.rs)
- Filesystem permissions scoped to $APPDATA/openpylon/**
- Tailwind CSS v4 via @tailwindcss/vite
- shadcn/ui initialized with 12 components
- All app dependencies: Zustand, zundo, dnd-kit, Framer Motion,
  Zod, ulid, date-fns, react-markdown, remark-gfm
- Path alias @/* configured in tsconfig + vite

src/App.tsx

@@ -0,0 +1,7 @@
+export default function App() {
+  return (
+    <div className="h-screen flex items-center justify-center bg-background text-foreground">
+      <h1 className="text-2xl font-bold">OpenPylon</h1>
+    </div>
+  );
+}