chore: setup TypeScript 6 and pnpm with mise

- Add mise.toml with pnpm latest
- Create root workspace with pnpm-workspace.yaml
- Upgrade TypeScript from 5.9.3 to 6.0.3 in apps/web
- Add vite-env.d.ts for CSS module type declarations
- Switch from npm to pnpm package management

apps/web/src/vite-env.d.ts

@@ -0,0 +1,6 @@
+/// <reference types="vite/client" />
+
+declare module "*.css" {
+  const content: string;
+  export default content;
+}