feat: 支持同一用户创建多个相同 leader 的跟单配置

- 删除 copy_trading 表的唯一约束 uk_account_leader
- 移除实体类 CopyTrading 的唯一约束注解
- 移除创建跟单时的重复检查逻辑
- 修改 Repository 方法 findByAccountIdAndLeaderId 返回列表而非单个对象
- 更新查询逻辑以支持返回多个跟单配置

现在允许同一用户对同一个 leader 创建多个不同配置的跟单关系。

backend/src/main/kotlin/com/wrbug/polymarketbot/entity/CopyTrading.kt

@@ -8,12 +8,7 @@ import com.wrbug.polymarketbot.util.toSafeBigDecimal
  * 跟单配置实体（独立配置，不再绑定模板）
  */
 @Entity
-@Table(
-    name = "copy_trading",
-    uniqueConstraints = [
-        UniqueConstraint(columnNames = ["account_id", "leader_id"])
-    ]
-)
+@Table(name = "copy_trading")
 data class CopyTrading(
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)

backend/src/main/kotlin/com/wrbug/polymarketbot/repository/CopyTradingRepository.kt

@@ -21,12 +21,12 @@ interface CopyTradingRepository : JpaRepository<CopyTrading, Long> {
     fun findByLeaderId(leaderId: Long): List<CopyTrading>
     
     /**
-     * 根据账户ID和Leader ID查找跟单
+     * 根据账户ID和Leader ID查找跟单列表
      */
     fun findByAccountIdAndLeaderId(
         accountId: Long,
         leaderId: Long
-    ): CopyTrading?
+    ): List<CopyTrading>
     
     /**
      * 查找所有启用的跟单

backend/src/main/kotlin/com/wrbug/polymarketbot/service/copytrading/configs/CopyTradingService.kt

@@ -50,16 +50,7 @@ class CopyTradingService(
             val leader = leaderRepository.findById(request.leaderId).orElse(null)
                 ?: return Result.failure(IllegalArgumentException("Leader 不存在"))
             
-            // 3. 检查是否已存在相同的跟单关系（accountId + leaderId）
-            val existing = copyTradingRepository.findByAccountIdAndLeaderId(
-                request.accountId,
-                request.leaderId
-            )
-            if (existing != null) {
-                return Result.failure(IllegalArgumentException("该跟单关系已存在"))
-            }
-            
-            // 4. 验证配置名（强校验：不能为空字符串）
+            // 3. 验证配置名（强校验：不能为空字符串）
             val configName = request.configName?.trim()
             if (configName.isNullOrBlank()) {
                 return Result.failure(IllegalArgumentException("配置名不能为空"))
@@ -286,11 +277,10 @@ class CopyTradingService(
         return try {
             val copyTradings = when {
                 request.accountId != null && request.leaderId != null -> {
-                    val found = copyTradingRepository.findByAccountIdAndLeaderId(
+                    copyTradingRepository.findByAccountIdAndLeaderId(
                         request.accountId,
                         request.leaderId
                     )
-                    if (found != null) listOf(found) else emptyList()
                 }
                 request.accountId != null -> {
                     copyTradingRepository.findByAccountId(request.accountId)

backend/src/main/resources/db/migration/V23__remove_unique_constraint_from_copy_trading.sql

@@ -0,0 +1,19 @@
+-- ============================================
+-- V23: 移除跟单关系的唯一约束
+-- 允许同一用户创建多个相同 leader 的跟单配置
+-- ============================================
+
+-- 删除唯一约束 uk_account_leader
+SET @uk_name = (SELECT CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS 
+                WHERE TABLE_SCHEMA = DATABASE() 
+                AND TABLE_NAME = 'copy_trading' 
+                AND CONSTRAINT_TYPE = 'UNIQUE' 
+                AND CONSTRAINT_NAME = 'uk_account_leader' 
+                LIMIT 1);
+SET @sql = IF(@uk_name IS NOT NULL, 
+              CONCAT('ALTER TABLE copy_trading DROP INDEX ', @uk_name), 
+              'SELECT 1');
+PREPARE stmt FROM @sql;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+