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

lib/pinball/tableSelectionStore.ts

@@ -0,0 +1,15 @@
+// In-memory handoff for a user-selected .vpx File between the landing page
+// and /play — a File can't survive a URL-based navigation, and this is a
+// single-shot value read once on mount, so module-level state is sufficient
+// (no need for anything heavier than a plain variable).
+let pendingFile: File | null = null;
+
+export function setPendingTable(file: File): void {
+  pendingFile = file;
+}
+
+export function takePendingTable(): File | null {
+  const file = pendingFile;
+  pendingFile = null;
+  return file;
+}