Fix auth token being clobbered by game seat token (userId always null)

The login JWT and the per-seat rejoin token shared the localStorage key
'shelem_token', so joining a game overwrote the auth token with the random
seat token. The socket then reconnected as an unauthenticated guest, so every
seat was recorded with userId=null and no stats or history were attributed.

- Seat token now uses its own key 'shelem_seat_token'; 'shelem_token' is auth-only
- Add GET /api/me + boot-time validateAuth() to drop stale/corrupted tokens
  instead of running as a "logged in" ghost
- reauthSocket() re-authenticates the live socket on login/register

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/app.js

@@ -471,10 +471,21 @@ function connectSocket(onReady) {
   if (!socket) {
     socket = io({ auth: { token: authToken } });
     initSocketHandlers();
+  } else {
+    // Reuse the socket but make sure it carries the current auth token
+    socket.auth = { token: authToken };
   }
   socket.once('connect', onReady);
 }
 
+// Re-authenticate an existing socket after login/register so the server sees
+// the user on this same connection (auth is only read at (re)connect time).
+function reauthSocket() {
+  if (!socket) return;
+  socket.auth = { token: authToken };
+  if (socket.connected) socket.disconnect().connect();
+}
+
 function initSocketHandlers() {
   // Persistent reconnect handler — auto-rejoin after any network drop mid-game
   socket.on('connect', () => {
@@ -555,20 +566,23 @@ function initSocketHandlers() {
 }
 
 // ─── Session persistence (localStorage so it survives tab/app close) ──────────
+// NOTE: the game-session (seat) token uses its OWN key. It must never share a
+// key with the auth JWT ('shelem_token'), or joining a game would overwrite the
+// login token and drop the player to an unauthenticated guest.
 function saveSession() {
-  localStorage.setItem('shelem_room',  myRoomId);
-  localStorage.setItem('shelem_seat',  mySeat);
-  localStorage.setItem('shelem_token', myToken);
+  localStorage.setItem('shelem_room',       myRoomId);
+  localStorage.setItem('shelem_seat',       mySeat);
+  localStorage.setItem('shelem_seat_token', myToken);
 }
 function clearSession() {
   localStorage.removeItem('shelem_room');
   localStorage.removeItem('shelem_seat');
-  localStorage.removeItem('shelem_token');
+  localStorage.removeItem('shelem_seat_token');
 }
 function tryRejoin() {
   const room  = localStorage.getItem('shelem_room');
   const seat  = localStorage.getItem('shelem_seat');
-  const token = localStorage.getItem('shelem_token');
+  const token = localStorage.getItem('shelem_seat_token');
   if (!room || seat === null || !token) return;
   // Set inside the callback so the persistent 'connect' handler doesn't
   // also emit rejoin on the very first connection (would be a duplicate)
@@ -1235,7 +1249,7 @@ async function doLogin() {
     localStorage.setItem('shelem_user',  authUser);
     hide('overlay-auth');
     updateAuthBar();
-    if (socket) socket.auth = { token: authToken };
+    reauthSocket();
   } catch { $('auth-login-error').textContent = 'Network error'; }
 }
 
@@ -1257,6 +1271,7 @@ async function doRegister() {
     localStorage.setItem('shelem_user',  authUser);
     hide('overlay-auth');
     updateAuthBar();
+    reauthSocket();
   } catch { $('auth-reg-error').textContent = 'Network error'; }
 }
 
@@ -1666,12 +1681,34 @@ function wireGameEvents() {
   });
 }
 
+// Validate the stored auth token before trusting it. Catches tokens that are
+// expired, or corrupted by the old localStorage key collision, so we don't run
+// around as a "logged in" ghost whose socket is actually an unauthenticated guest.
+async function validateAuth() {
+  if (!authToken) return;
+  try {
+    const r = await fetch('/api/me', { headers: { Authorization: `Bearer ${authToken}` } });
+    if (!r.ok) throw new Error('invalid');
+    const d = await r.json();
+    authUser = d.username;
+    localStorage.setItem('shelem_user', authUser);
+  } catch {
+    authToken = null; authUser = null;
+    localStorage.removeItem('shelem_token');
+    localStorage.removeItem('shelem_user');
+  }
+  updateAuthBar();
+}
+
 // ─── Boot ─────────────────────────────────────────────────────
-document.addEventListener('DOMContentLoaded', () => {
+document.addEventListener('DOMContentLoaded', async () => {
   initLobby();
   wireGameEvents();
   applyBarBottom();
 
+  // Drop any stale/corrupted auth token before we use it to connect
+  await validateAuth();
+
   // Pre-fill name from auth
   if (authUser) $('input-name').value = authUser;