feat: add admin dashboard backend and deployment workflow

src/main/kotlin/me/wypark/blogbackend/api/controller/admin/AdminDashboardController.kt

@@ -0,0 +1,26 @@
+package me.wypark.blogbackend.api.controller.admin
+
+import me.wypark.blogbackend.api.common.ApiResponse
+import me.wypark.blogbackend.api.dto.AdminDashboardResponse
+import me.wypark.blogbackend.domain.dashboard.AdminDashboardService
+import org.springframework.http.ResponseEntity
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RequestMapping
+import org.springframework.web.bind.annotation.RequestParam
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+@RequestMapping("/api/admin/dashboard")
+class AdminDashboardController(
+    private val adminDashboardService: AdminDashboardService
+) {
+
+    @GetMapping
+    fun getDashboard(
+        @RequestParam(required = false) range: String?,
+        @RequestParam(required = false) timezone: String?
+    ): ResponseEntity<ApiResponse<AdminDashboardResponse>> {
+        val dashboard = adminDashboardService.getDashboard(range, timezone)
+        return ResponseEntity.ok(ApiResponse.success(dashboard, "OK"))
+    }
+}

src/main/kotlin/me/wypark/blogbackend/api/dto/AdminDashboardDtos.kt

@@ -0,0 +1,89 @@
+package me.wypark.blogbackend.api.dto
+
+import java.math.BigDecimal
+import java.time.LocalDate
+import java.time.OffsetDateTime
+
+data class DashboardMetric(
+    val value: Long,
+    val previousValue: Long? = null,
+    val changeRate: BigDecimal? = null
+)
+
+data class DashboardOverview(
+    val todayViews: DashboardMetric,
+    val weekViews: DashboardMetric,
+    val monthViews: DashboardMetric,
+    val totalPosts: Long,
+    val totalComments: Long,
+    val totalCategories: Long,
+    val lastPublishedAt: OffsetDateTime?,
+    val generatedAt: OffsetDateTime
+)
+
+data class DashboardTrafficPoint(
+    val date: LocalDate,
+    val views: Long
+)
+
+data class DashboardPostStat(
+    val id: Long,
+    val title: String,
+    val slug: String,
+    val categoryName: String,
+    val viewCount: Long,
+    val rangeViewCount: Long,
+    val commentCount: Long,
+    val createdAt: OffsetDateTime,
+    val updatedAt: OffsetDateTime?
+)
+
+data class DashboardCategoryStat(
+    val id: Long,
+    val name: String,
+    val parentId: Long?,
+    val postCount: Long,
+    val viewCount: Long,
+    val recentViewCount: Long,
+    val lastPublishedAt: OffsetDateTime?,
+    val childrenCount: Long
+)
+
+data class DashboardActionItems(
+    val unansweredComments: Long,
+    val uncategorizedPosts: Long,
+    val stalePopularPosts: Long
+)
+
+data class DashboardPostSummary(
+    val id: Long,
+    val title: String,
+    val slug: String,
+    val categoryName: String,
+    val viewCount: Long,
+    val createdAt: OffsetDateTime,
+    val tags: List<String>
+)
+
+data class AdminDashboardCommentSummary(
+    val id: Long,
+    val content: String,
+    val author: String?,
+    val guestNickname: String?,
+    val memberNickname: String?,
+    val postSlug: String?,
+    val postTitle: String?,
+    val createdAt: OffsetDateTime
+)
+
+data class AdminDashboardResponse(
+    val overview: DashboardOverview,
+    val traffic: List<DashboardTrafficPoint>,
+    val topPosts: List<DashboardPostStat>,
+    val risingPosts: List<DashboardPostStat>,
+    val stalePopularPosts: List<DashboardPostStat>,
+    val recentPosts: List<DashboardPostSummary>,
+    val recentComments: List<AdminDashboardCommentSummary>,
+    val categoryStats: List<DashboardCategoryStat>,
+    val actionItems: DashboardActionItems
+)