fix: 🐛 修复系统配置页保存配置的bug

backend/src/services/ConfigService.ts

@@ -69,11 +69,25 @@ export class ConfigService {
    */
   async update(key: string, value: string, description?: string) {
     try {
-      // 更新数据库
-      await this.configRepository.upsert(
-        { key, value, description },
-        ['key']
-      )
+      // 先查找记录是否存在
+      const existingConfig = await this.configRepository.findOne({ where: { key } })
+      
+      if (existingConfig) {
+        // 记录存在，更新它
+        existingConfig.value = value
+        if (description !== undefined) {
+          existingConfig.description = description
+        }
+        await this.configRepository.save(existingConfig)
+      } else {
+        // 记录不存在，创建新记录
+        const newConfig = this.configRepository.create({
+          key,
+          value,
+          description
+        })
+        await this.configRepository.save(newConfig)
+      }
 
       // 更新缓存
       this.configCache[key] = value