feat: add date range filter to marketing list API

Added start_date, end_date, and filter_by query parameters to the
GET /api/marketing/ endpoint. Users can now filter marketing records
by a date range using either so_date (Sales Order date, default) or
created_at as the target column.

Changes:
- validation: added StartDate, EndDate (YYYY-MM-DD format), and
  FilterBy (oneof: so_date, created_at) to DeliveryOrderQuery struct
- controller: parse the three new query params in GetAll handler
- service: apply >=start / <end+1day date range filter in the query
  modifier using the existing utils.ParseDateRangeForQuery helper

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/modules/marketing/validations/deliveryorder.validation.go

@@ -34,6 +34,9 @@ type DeliveryOrderQuery struct {
 	WarehouseID           uint   `query:"warehouse_id" validate:"omitempty,gt=0"`
 	SortBy                string `query:"sort_by" validate:"omitempty,oneof=so_number so_date status customer grand_total created_at"`
 	SortOrder             string `query:"sort_order" validate:"omitempty,oneof=asc desc"`
+	StartDate             string `query:"start_date" validate:"omitempty,datetime=2006-01-02"`
+	EndDate               string `query:"end_date" validate:"omitempty,datetime=2006-01-02"`
+	FilterBy              string `query:"filter_by" validate:"omitempty,oneof=so_date created_at"`
 }
 
 type DeliveryOrderApprove struct {