feat: 가계부·게시판 백엔드 API 구현

- com.sb.web 패키지로 재구성: account / auth / board / user / admin / common
- 가계부(account): 내역(필터), 계좌·순자산, 예산, 분류, 정기 거래, 투자 포트폴리오
  (종목·매매 이력, 이동평균 평단·실현/평가손익)
- MyBatis + MariaDB + Redis 세션, BCrypt
- 스키마 자동 초기화(db/*.sql, 멱등), 사용자별 데이터 격리(member_id)
- 문서: docs/BACKEND.md, .env.example

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

src/main/java/com/sb/web/admin/controller/AdminTagController.java

@@ -0,0 +1,83 @@
+package com.sb.web.admin.controller;
+
+import com.sb.web.board.dto.BoardSettingRequest;
+import com.sb.web.board.dto.BoardSettingResponse;
+import com.sb.web.board.dto.TagCategoryRequest;
+import com.sb.web.board.dto.TagCategoryResponse;
+import com.sb.web.board.dto.TagRequest;
+import com.sb.web.board.dto.TagResponse;
+import com.sb.web.board.service.TagService;
+import jakarta.validation.Valid;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+/**
+ * 관리자 태그 관리 API. (/api/admin/** — AdminInterceptor 로 ADMIN 권한 필요)
+ *   GET    /tag-categories            카테고리+태그 목록
+ *   POST   /tag-categories            카테고리 생성
+ *   PUT    /tag-categories/{id}       카테고리 수정
+ *   DELETE /tag-categories/{id}       카테고리 삭제(소속 태그 포함)
+ *   POST   /tags                      태그 생성
+ *   PUT    /tags/{id}                 태그 수정
+ *   DELETE /tags/{id}                 태그 삭제
+ */
+@RestController
+@RequestMapping("/api/admin")
+@RequiredArgsConstructor
+public class AdminTagController {
+
+    private final TagService tagService;
+
+    @GetMapping("/tag-categories")
+    public List<TagCategoryResponse> categories() {
+        return tagService.listGrouped();
+    }
+
+    @PostMapping("/tag-categories")
+    public ResponseEntity<TagCategoryResponse> createCategory(@Valid @RequestBody TagCategoryRequest req) {
+        return ResponseEntity.status(HttpStatus.CREATED).body(tagService.createCategory(req));
+    }
+
+    @PutMapping("/tag-categories/{id}")
+    public TagCategoryResponse updateCategory(@PathVariable Long id, @Valid @RequestBody TagCategoryRequest req) {
+        return tagService.updateCategory(id, req);
+    }
+
+    @DeleteMapping("/tag-categories/{id}")
+    public ResponseEntity<Void> deleteCategory(@PathVariable Long id) {
+        tagService.deleteCategory(id);
+        return ResponseEntity.noContent().build();
+    }
+
+    @PostMapping("/tags")
+    public ResponseEntity<TagResponse> createTag(@Valid @RequestBody TagRequest req) {
+        return ResponseEntity.status(HttpStatus.CREATED).body(tagService.createTag(req));
+    }
+
+    @PutMapping("/tags/{id}")
+    public TagResponse updateTag(@PathVariable Long id, @Valid @RequestBody TagRequest req) {
+        return tagService.updateTag(id, req);
+    }
+
+    @DeleteMapping("/tags/{id}")
+    public ResponseEntity<Void> deleteTag(@PathVariable Long id) {
+        tagService.deleteTag(id);
+        return ResponseEntity.noContent().build();
+    }
+
+    /* ===== 게시판 설정 (사용할 태그 카테고리) ===== */
+
+    @GetMapping("/board-setting")
+    public BoardSettingResponse boardSetting() {
+        return tagService.getBoardSetting();
+    }
+
+    @PutMapping("/board-setting")
+    public BoardSettingResponse updateBoardSetting(@RequestBody BoardSettingRequest req) {
+        return tagService.setBoardSetting(req.getTagCategoryId());
+    }
+}