feat: 게시판 공지 기능 (관리자) — 목록 최상단 고정

- post.notice 컬럼 추가(멱등 ALTER)
- 목록 정렬 ORDER BY notice DESC, id DESC (공지 최상단)
- 작성 시 공지 설정(관리자만 반영) + /posts/{id}/notice·unnotice 토글
- Post/PostSummary/PostDetail/PostRequest 에 notice 반영

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/java/com/sb/web/board/controller/BoardController.java

@@ -99,6 +99,24 @@ public class BoardController {
         return ResponseEntity.noContent().build();
     }
 
+    /** 공지 등록 (관리자) — 목록 최상단 고정 */
+    @PostMapping("/posts/{id}/notice")
+    public ResponseEntity<Void> notice(
+            @PathVariable Long id,
+            @RequestAttribute(AuthInterceptor.CURRENT_MEMBER) SessionUser current) {
+        boardService.setNotice(id, true, current);
+        return ResponseEntity.noContent().build();
+    }
+
+    /** 공지 해제 (관리자) */
+    @PostMapping("/posts/{id}/unnotice")
+    public ResponseEntity<Void> unnotice(
+            @PathVariable Long id,
+            @RequestAttribute(AuthInterceptor.CURRENT_MEMBER) SessionUser current) {
+        boardService.setNotice(id, false, current);
+        return ResponseEntity.noContent().build();
+    }
+
     @GetMapping("/tags")
     public List<String> tags() {
         return boardService.allTags();

src/main/java/com/sb/web/board/domain/Post.java

@@ -25,6 +25,7 @@ public class Post implements Serializable {
     private Integer viewCount;
     private Boolean blocked;
     private String blockReason;
+    private Boolean notice; // 공지(상단 고정) — 관리자만 설정
     private String category; // 게시판 구분: community/saving/tips
     private LocalDateTime createdAt;
     private LocalDateTime updatedAt;

src/main/java/com/sb/web/board/dto/PostDetail.java

@@ -22,6 +22,7 @@ public class PostDetail {
     private Integer viewCount;
     private Boolean blocked;
     private String blockReason;
+    private Boolean notice;
     private String category;
     private LocalDateTime createdAt;
     private LocalDateTime updatedAt;
@@ -38,6 +39,7 @@ public class PostDetail {
                 .viewCount(p.getViewCount())
                 .blocked(Boolean.TRUE.equals(p.getBlocked()))
                 .blockReason(p.getBlockReason())
+                .notice(Boolean.TRUE.equals(p.getNotice()))
                 .category(p.getCategory())
                 .createdAt(p.getCreatedAt())
                 .updatedAt(p.getUpdatedAt())
@@ -54,6 +56,7 @@ public class PostDetail {
                 .authorName(p.getAuthorName())
                 .viewCount(p.getViewCount())
                 .blocked(true)
+                .notice(Boolean.TRUE.equals(p.getNotice()))
                 .category(p.getCategory())
                 .createdAt(p.getCreatedAt())
                 .tags(List.of())

src/main/java/com/sb/web/board/dto/PostRequest.java

@@ -22,6 +22,9 @@ public class PostRequest {
     /** 게시판 구분: community/saving/tips. 없으면 community */
     private String category;
 
+    /** 공지 등록 여부 (관리자만 반영). 작성 시 선택 */
+    private Boolean notice;
+
     /** 선택한 태그 ID 목록 (DB에 등록된 태그만, 선택) */
     private List<Long> tagIds;
 }

src/main/java/com/sb/web/board/dto/PostSummary.java

@@ -17,6 +17,7 @@ public class PostSummary {
     private Integer viewCount;
     private Integer commentCount;
     private Boolean blocked;
+    private Boolean notice;
     private LocalDateTime createdAt;
     private List<String> tags;
 }

src/main/java/com/sb/web/board/mapper/PostMapper.java

@@ -35,4 +35,7 @@ public interface PostMapper {
     int updateBlocked(@Param("id") Long id,
                       @Param("blocked") boolean blocked,
                       @Param("blockReason") String blockReason);
+
+    int updateNotice(@Param("id") Long id,
+                     @Param("notice") boolean notice);
 }

src/main/java/com/sb/web/board/service/BoardService.java

@@ -91,6 +91,14 @@ public class BoardService {
         postMapper.updateBlocked(id, blocked, blocked ? reason : null);
     }
 
+    /** 게시글 공지 설정/해제 (관리자 전용) — 목록 최상단 고정 */
+    @Transactional
+    public void setNotice(Long id, boolean notice, SessionUser user) {
+        assertAdmin(user);
+        mustFindPost(id);
+        postMapper.updateNotice(id, notice);
+    }
+
     /** Redis 로 (사용자, 게시글) 단위 첫 열람 여부 판단 → 중복 클릭 시 조회수 증가 방지 */
     private boolean shouldCountView(Long postId, SessionUser viewer) {
         if (viewer == null) {
@@ -108,6 +116,8 @@ public class BoardService {
                 .content(req.getContent())
                 .authorId(author.getId())
                 .authorName(author.getName())
+                // 공지는 관리자만 설정 가능
+                .notice(isAdmin(author) && Boolean.TRUE.equals(req.getNotice()))
                 .category(toCategory(req.getCategory()))
                 .build();
         postMapper.insert(post);