Add vpinball: a browser Visual Pinball player

Next.js app that plays real .vpx tables via @valknar/vpinball-wasm
(WebAssembly Visual Pinball). Demo mode with the bundled default
table, drag-and-drop custom table upload, a cabinet-styled UI with a
coin-door HUD (fullscreen/stats/info/eject), a custom 404 page, PWA
support (hand-rolled service worker), and a static Docker Compose
deployment behind nginx.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012hQoM3jJT1Lx7CMTciMzvD

public/sw.js

@@ -0,0 +1,77 @@
+// Bump this on every release that changes the app shell or the vendored
+// engine build — it's the only thing that invalidates old caches, since
+// none of the cached URLs below are content-hashed by us.
+const CACHE_VERSION = "v1";
+const SHELL_CACHE = `shell-${CACHE_VERSION}`;
+const ENGINE_CACHE = `engine-${CACHE_VERSION}`;
+
+const SHELL_ASSETS = [
+  "/",
+  "/play/",
+  "/404.html",
+  "/manifest.webmanifest",
+  "/icons/icon-192.png",
+  "/icons/icon-512.png",
+];
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(
+    caches
+      .open(SHELL_CACHE)
+      .then((cache) => cache.addAll(SHELL_ASSETS))
+      .then(() => self.skipWaiting()),
+  );
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    caches
+      .keys()
+      .then((keys) =>
+        Promise.all(
+          keys
+            .filter((key) => key !== SHELL_CACHE && key !== ENGINE_CACHE)
+            .map((key) => caches.delete(key)),
+        ),
+      )
+      .then(() => self.clients.claim()),
+  );
+});
+
+self.addEventListener("fetch", (event) => {
+  const url = new URL(event.request.url);
+  if (event.request.method !== "GET" || url.origin !== self.location.origin) return;
+
+  // The engine's .wasm/.data/.js are large and effectively immutable per
+  // release (they aren't content-hashed), so once fetched they're served
+  // straight from cache — cache-busting happens by bumping CACHE_VERSION.
+  if (url.pathname.startsWith("/vendor/vpinball-wasm/")) {
+    event.respondWith(
+      caches.open(ENGINE_CACHE).then((cache) =>
+        cache.match(event.request).then(
+          (hit) =>
+            hit ??
+            fetch(event.request).then((response) => {
+              cache.put(event.request, response.clone());
+              return response;
+            }),
+        ),
+      ),
+    );
+    return;
+  }
+
+  event.respondWith(
+    caches.match(event.request).then(
+      (hit) =>
+        hit ??
+        fetch(event.request).then((response) => {
+          if (response.ok) {
+            const clone = response.clone();
+            caches.open(SHELL_CACHE).then((cache) => cache.put(event.request, clone));
+          }
+          return response;
+        }),
+    ),
+  );
+});