refactor impstr to react/vite stack, update deploy target

migrate from vanilla TypeScript + Bun bundler to React 19, Vite, TanStack Router,
Zustand, shadcn-style components, Tailwind v4, vite-plugin-pwa.

game logic moves into a Zustand store, UI into React feature components with
file-based routing. all 27 tests pass, biome lint clean.

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

src/shared/lib/utils.ts

@@ -0,0 +1,6 @@
+import { type ClassValue, clsx } from "clsx";
+import { twMerge } from "tailwind-merge";
+
+export function cn(...inputs: ClassValue[]) {
+	return twMerge(clsx(inputs));
+}