fix: startOfQuater 메서드를 Core로 이동함으로서 여러 곳에서 사용 가능하도록 처리

Author: opficdev

…WidgetCore/Sources/Common/Calendar.swift …cation/DevLogCore/Sources/Calendar.swiftWidget/DevLogWidgetCore/Sources/Common/Calendar.swift renamed to Application/DevLogCore/Sources/Calendar.swift Widget/DevLogWidgetCore/Sources/Common/Calendar.swift renamed to Application/DevLogCore/Sources/Calendar.swift

@@ -1,6 +1,6 @@
 //
 //  Calendar.swift
-//  DevLogWidgetCore
+//  DevLogCore
 //
 //  Created by opfic on 4/30/26.
 //

Widget/DevLogWidgetCore/Sources/Common/WidgetHeatmapPlaceholderShape.swift

@@ -6,6 +6,7 @@
 //
 
 import Foundation
+import DevLogCore
 
 public struct WidgetHeatmapPlaceholderShape {
     public let currentMonths: [WidgetHeatmapPlaceholderMonthShape]