feat: 用户名密码登录注册系统

- 新增 /api/auth/register 和 /api/auth/login 接口，使用 bcryptjs 哈希密码
- User 模型改为 username + passwordHash，id 自动生成 cuid
- 新增 AuthModal 组件（登录/注册双标签页），替换旧的 ProfileSetupModal
- 重写 /profile 页面：支持修改用户名、密码、头像、绑定邮箱、退出登录
- /api/user PUT 支持密码修改（需验证当前密码）和用户名唯一性校验
- 游客模式保留，右上角显示"登录"按钮；登录后显示头像和用户名
- 全局 nickname -> username 重命名（types、SwipeDeck、RoomManageModal、buildRoomStatus）
- 新增 logout() 清除登录态并重新生成游客 UUID

src/components/RoomManageModal.tsx

@@ -11,29 +11,8 @@ import {
   Crown,
   Loader2,
 } from "lucide-react";
-
-const AVATARS = [
-  { emoji: "🐱", bg: "bg-amber-100" },
-  { emoji: "🐶", bg: "bg-orange-100" },
-  { emoji: "🦊", bg: "bg-red-100" },
-  { emoji: "🐰", bg: "bg-pink-100" },
-  { emoji: "🐼", bg: "bg-zinc-100" },
-  { emoji: "🐨", bg: "bg-sky-100" },
-  { emoji: "🦁", bg: "bg-yellow-100" },
-  { emoji: "🐸", bg: "bg-lime-100" },
-  { emoji: "🐵", bg: "bg-stone-100" },
-  { emoji: "🐷", bg: "bg-rose-100" },
-  { emoji: "🐙", bg: "bg-purple-100" },
-  { emoji: "🦄", bg: "bg-violet-100" },
-] as const;
-
-function getAvatar(uid: string) {
-  let hash = 0;
-  for (let i = 0; i < uid.length; i++) {
-    hash = (hash * 31 + uid.charCodeAt(i)) | 0;
-  }
-  return AVATARS[((hash % AVATARS.length) + AVATARS.length) % AVATARS.length];
-}
+import { UserProfile } from "@/types";
+import { getAvatar, getAvatarBg } from "@/lib/avatars";
 
 interface RoomManageModalProps {
   open: boolean;
@@ -44,6 +23,7 @@ interface RoomManageModalProps {
   locked: boolean;
   swipeCounts: Record<string, number>;
   totalCards: number;
+  userProfiles: Record<string, UserProfile>;
   onToast: (msg: string) => void;
 }
 
@@ -56,6 +36,7 @@ export default function RoomManageModal({
   locked,
   swipeCounts,
   totalCards,
+  userProfiles,
   onToast,
 }: RoomManageModalProps) {
   const backdropRef = useRef<HTMLDivElement>(null);
@@ -172,7 +153,10 @@ export default function RoomManageModal({
               </h3>
               <div className="mt-2 flex flex-col gap-1.5">
                 {users.map((uid) => {
-                  const avatar = getAvatar(uid);
+                  const profile = userProfiles[uid];
+                  const emoji = profile?.avatar ?? getAvatar(uid).emoji;
+                  const bg = profile ? getAvatarBg(profile.avatar) : getAvatar(uid).bg;
+                  const displayName = profile?.username ?? uid.slice(0, 8);
                   const isCreator = uid === userId;
                   const swiped = swipeCounts[uid] ?? 0;
                   const finished = swiped >= totalCards;
@@ -183,9 +167,9 @@ export default function RoomManageModal({
                       className="flex items-center gap-2.5 rounded-xl bg-zinc-50 px-3 py-2.5"
                     >
                       <span
-                        className={`inline-flex h-8 w-8 items-center justify-center rounded-full text-base ${avatar.bg}`}
+                        className={`inline-flex h-8 w-8 items-center justify-center rounded-full text-base ${bg}`}
                       >
-                        {avatar.emoji}
+                        {emoji}
                       </span>
                       <div className="flex min-w-0 flex-1 flex-col">
                         <div className="flex items-center gap-1.5">
@@ -196,7 +180,7 @@ export default function RoomManageModal({
                             </span>
                           )}
                           <span className="truncate text-xs font-medium text-zinc-500">
-                            {uid.slice(0, 8)}
+                            {displayName}
                           </span>
                         </div>
                         <span