[FEAT/#120] 어드민 메인 대시보드 조회 API 구현 및 API 연결용 임시 MOCK API 추가

[ckkim817]

💡 Issue

• resolved: [FEAT] 어드민 메인 대시보드 조회 API 구현 및 API 연결용 임시 MOCK API 추가 #120

📄 Description

• 어드민 메인 대시보드 조회 API 구현하고, API 연결용 임시 MOCK API들을 추가했습니다. 해당 임시 API들은 추후 삭제할 예정입니다.

[Copilot]

Pull Request Overview

This PR implements an admin main dashboard API and adds temporary mock APIs for API integration testing. The dashboard displays the count of pending spots for admin monitoring purposes.

• Implements admin dashboard API to retrieve pending spot counts
• Adds repository method to count spots by status
• Creates temporary mock APIs for spots listing and detail views

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
SpotRepository.java	Adds count method for spots by status
AdminService.java	New service implementing dashboard logic
DashboardResponse.java	Response DTO for dashboard data
AdminController.java	Adds dashboard endpoint and mock APIs

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