feat(budget): 1회성 예산 API 추가

- BudgetOnetime 도메인/DTO/Mapper/Service 신규
- BudgetController: GET/POST/PUT/DELETE /api/account/budgets/onetime 엔드포인트 추가
- account.sql: budget_onetime 테이블 CREATE TABLE IF NOT EXISTS 추가
- WalletRequest: MINUS 유형 허용 추가
- CategoryService: importDefaults, validateParent, ensureCategory 추가

※ 최초 배포 시 서버 .env에 SQL_INIT_MODE=always 추가 후 재시작 필요 (budget_onetime 테이블 생성)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/java/com/sb/web/account/service/BudgetOnetimeService.java

@@ -0,0 +1,82 @@
+package com.sb.web.account.service;
+
+import com.sb.web.account.domain.BudgetOnetime;
+import com.sb.web.account.dto.BudgetOnetimeRequest;
+import com.sb.web.account.dto.BudgetOnetimeResponse;
+import com.sb.web.account.mapper.BudgetOnetimeMapper;
+import com.sb.web.common.exception.ApiException;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Service
+@RequiredArgsConstructor
+public class BudgetOnetimeService {
+
+    private final BudgetOnetimeMapper mapper;
+
+    public List<BudgetOnetimeResponse> list(Long memberId) {
+        return mapper.findByMember(memberId).stream()
+                .map(b -> {
+                    long spent = mapper.sumExpenseInRange(
+                            memberId, b.getStartDate(), b.getEndDate(), b.getCategory());
+                    return BudgetOnetimeResponse.from(b, spent);
+                })
+                .toList();
+    }
+
+    @Transactional
+    public BudgetOnetimeResponse create(BudgetOnetimeRequest req, Long memberId) {
+        validate(req);
+        BudgetOnetime b = BudgetOnetime.builder()
+                .memberId(memberId)
+                .title(req.getTitle().trim())
+                .category(blankToNull(req.getCategory()))
+                .amount(req.getAmount())
+                .startDate(req.getStartDate())
+                .endDate(req.getEndDate())
+                .build();
+        mapper.insert(b);
+        long spent = mapper.sumExpenseInRange(memberId, b.getStartDate(), b.getEndDate(), b.getCategory());
+        return BudgetOnetimeResponse.from(b, spent);
+    }
+
+    @Transactional
+    public BudgetOnetimeResponse update(Long id, BudgetOnetimeRequest req, Long memberId) {
+        validate(req);
+        BudgetOnetime b = mustFind(id, memberId);
+        b.setTitle(req.getTitle().trim());
+        b.setCategory(blankToNull(req.getCategory()));
+        b.setAmount(req.getAmount());
+        b.setStartDate(req.getStartDate());
+        b.setEndDate(req.getEndDate());
+        mapper.update(b);
+        long spent = mapper.sumExpenseInRange(memberId, b.getStartDate(), b.getEndDate(), b.getCategory());
+        return BudgetOnetimeResponse.from(b, spent);
+    }
+
+    @Transactional
+    public void delete(Long id, Long memberId) {
+        mustFind(id, memberId);
+        mapper.delete(id, memberId);
+    }
+
+    private void validate(BudgetOnetimeRequest req) {
+        if (req.getEndDate().isBefore(req.getStartDate())) {
+            throw new ApiException(HttpStatus.BAD_REQUEST, "종료일이 시작일보다 빠를 수 없습니다.");
+        }
+    }
+
+    private BudgetOnetime mustFind(Long id, Long memberId) {
+        BudgetOnetime b = mapper.findByIdAndMember(id, memberId);
+        if (b == null) throw new ApiException(HttpStatus.NOT_FOUND, "1회성 예산을 찾을 수 없습니다.");
+        return b;
+    }
+
+    private String blankToNull(String s) {
+        return (s == null || s.isBlank()) ? null : s.trim();
+    }
+}