feat(web): add zustand stores and Socket.IO client

Implements ship list store (REST-based) and ship detail store (Socket.IO-based)
with room join/leave, reconnection handling, and real-time event listeners.

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

web/src/socket.ts

@@ -0,0 +1,13 @@
+import { io } from 'socket.io-client';
+
+// In development, Vite proxies /socket.io to the server.
+// In production, both are served from the same origin.
+const socket = io({
+  autoConnect: true,
+  reconnection: true,
+  reconnectionAttempts: Infinity,
+  reconnectionDelay: 1000,
+  reconnectionDelayMax: 5000,
+});
+
+export default socket;