feat: 添加分页功能和缓存管理，优化问答记录展示

prisma/schema.prisma

@@ -13,17 +13,19 @@ datasource db {
 // Better Auth 标准用户表
 // apiToken 由服务端注册 hook 生成，供 OCS 油猴脚本跨域身份验证
 model User {
-  id            String     @id
-  name          String
-  email         String     @unique
-  emailVerified Boolean
-  image         String?
-  createdAt     DateTime
-  updatedAt     DateTime
-  apiToken      String?    @unique
-  sessions      Session[]
-  accounts      Account[]
-  qaRecords     QaRecord[]
+  id             String     @id
+  name           String
+  email          String     @unique
+  emailVerified  Boolean
+  image          String?
+  createdAt      DateTime
+  updatedAt      DateTime
+  apiToken       String?    @unique
+  /// 用户最近一次清缓存的时间；只有在此时间之后写入的记录才算缓存命中
+  cacheClearedAt DateTime?
+  sessions       Session[]
+  accounts       Account[]
+  qaRecords      QaRecord[]
 
   @@map("user")
 }
@@ -85,7 +87,10 @@ model QaRecord {
   type      String
   options   String?  @db.Text
   answer    String?  @db.Text
+  /// 题目+题型+选项的 MD5，用于 DB 缓存查询；老记录为 null
+  hash      String?  @db.Char(32)
   createdAt DateTime @default(now())
 
+  @@index([userId, hash])
   @@map("qa_record")
 }