fix(supply-api): 修复编译错误和测试问题

- 添加 ErrNotFound 和 ErrConcurrencyConflict 错误定义
- 修复 pgx.NullTime 替换为 *time.Time
- 修复 db.go 事务类型 (pgx.Tx vs pgxpool.Tx)
- 移除未使用的导入和变量
- 修复 NewSupplyAPI 调用参数
- 修复中间件链路 handler 类型问题
- 修复适配器类型引用 (storage.InMemoryAccountStore 等)
- 所有测试通过

Test: go test ./...

supply-api/internal/repository/idempotency.go

@@ -16,8 +16,8 @@ type IdempotencyStatus string
 
 const (
 	IdempotencyStatusProcessing IdempotencyStatus = "processing"
-	IdempotencyStatusSucceeded IdempotencyStatus = "succeeded"
-	IdempotencyStatusFailed    IdempotencyStatus = "failed"
+	IdempotencyStatusSucceeded  IdempotencyStatus = "succeeded"
+	IdempotencyStatusFailed     IdempotencyStatus = "failed"
 )
 
 // IdempotencyRecord 幂等记录