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

package-lock.json

@@ -9,6 +9,7 @@
       "version": "0.1.0",
       "dependencies": {
         "@prisma/client": "^6.19.2",
+        "bcryptjs": "^3.0.3",
         "canvas-confetti": "^1.9.4",
         "framer-motion": "^12.34.3",
         "lucide-react": "^0.575.0",
@@ -21,6 +22,7 @@
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
+        "@types/bcryptjs": "^2.4.6",
         "@types/canvas-confetti": "^1.9.0",
         "@types/node": "^20",
         "@types/react": "^19",
@@ -1618,6 +1620,13 @@
         "tslib": "^2.4.0"
       }
     },
+    "node_modules/@types/bcryptjs": {
+      "version": "2.4.6",
+      "resolved": "https://registry.npmjs.org/@types/bcryptjs/-/bcryptjs-2.4.6.tgz",
+      "integrity": "sha512-9xlo6R2qDs5uixm0bcIqCeMCE6HiQsIyel9KQySStiyqNl2tnj2mP3DX1Nf56MD6KMenNNlBBsy3LJ7gUEQPXQ==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/canvas-confetti": {
       "version": "1.9.0",
       "resolved": "https://registry.npmjs.org/@types/canvas-confetti/-/canvas-confetti-1.9.0.tgz",
@@ -2548,6 +2557,15 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/bcryptjs": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/bcryptjs/-/bcryptjs-3.0.3.tgz",
+      "integrity": "sha512-GlF5wPWnSa/X5LKM1o0wz0suXIINz1iHRLvTS+sLyi7XPbe5ycmYI3DlZqVGZZtDgl4DmasFg7gOB3JYbphV5g==",
+      "license": "BSD-3-Clause",
+      "bin": {
+        "bcrypt": "bin/bcrypt"
+      }
+    },
     "node_modules/brace-expansion": {
       "version": "1.1.12",
       "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.12.tgz",