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/vite-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="vite/client" />