fix: avatar upload during registration completes before redirect

Registration avatar upload raced with AuthRedirect — setting the Zustand
token triggered navigation before the upload could finish. Now the token
is stored in localStorage (for API auth) but not in Zustand until the
avatar upload completes, so the page stays mounted throughout.

Extracts initSession() from login/register for reuse.

packages/web/src/components/auth/RegisterPage.tsx

@@ -40,8 +40,7 @@ export function RegisterPage() {
   const [isRegistering, setIsRegistering] = useState(false);
   const [retryAfter, setRetryAfter] = useState(0);
 
-  const register = useAuthStore((s) => s.register);
-  const updateProfile = useAuthStore((s) => s.updateProfile);
+  const initSession = useAuthStore((s) => s.initSession);
   const navigate = useNavigate();
   const [searchParams] = useSearchParams();
   const redirect = searchParams.get('redirect');
@@ -192,18 +191,28 @@ export function RegisterPage() {
     try {
       const dn = skip ? undefined : displayName.trim() || undefined;
       const ac = skip ? undefined : avatarColor;
-      await register(username.trim(), password, dn, ac);
 
-      // Upload avatar if chosen (non-fatal — account already created)
+      // Step 1: Register via API — store token in localStorage for API auth,
+      // but NOT in Zustand yet so AuthRedirect doesn't fire prematurely
+      const response = await api.auth.register({
+        username: username.trim(), password, displayName: dn, avatarColor: ac,
+      });
+      localStorage.setItem('backspace_token', response.token);
+
+      // Step 2: Upload avatar while still on the register page
+      let finalUser = response.user;
       if (!skip && avatarFile) {
         try {
           const attachment = await api.uploads.upload(avatarFile);
-          await updateProfile({ avatar: attachment.filename });
+          finalUser = await api.users.update({ avatar: attachment.filename });
         } catch {
           // Avatar upload failed — user can set it later in settings
         }
       }
 
+      // Step 3: Activate session — sets Zustand token, triggers AuthRedirect
+      initSession(response.token, finalUser);
+
       if (redirect && redirect.startsWith('/') && !redirect.startsWith('//')) {
         navigate(redirect);
       } else {