refactor: 提取公共分页解析函数 parsePageAndSize

- 新增 internal/api/handler/common.go 存放 handler 层公共辅助函数
- parsePageAndSize: 统一提取 page/page_size 参数解析、默认值设置、ClampPageSize 调用
- device/log/webhook handler: 替换重复的分页解析代码为 parsePageAndSize 调用
- 清理不再需要的 strconv/pagination 导入

internal/api/handler/common.go

@@ -0,0 +1,21 @@
+package handler
+
+import (
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/user-management-system/internal/pagination"
+)
+
+// parsePageAndSize extracts and validates page & page_size from query parameters.
+// Returns page (>=1) and pageSize (clamped to [1, MaxPageSize]).
+func parsePageAndSize(c *gin.Context) (page, pageSize int) {
+	page, _ = strconv.Atoi(c.DefaultQuery("page", "1"))
+	if page < 1 {
+		page = 1
+	}
+	pageSize, _ = strconv.Atoi(c.DefaultQuery("page_size", strconv.Itoa(pagination.DefaultPageSize)))
+	pageSize = pagination.ClampPageSize(pageSize)
+	return
+}