feat: 계약 승계(contract succession) — 유지수수료 귀속 후임 전환 (V86)

설계사 해촉/이관 시 보험계약의 유지수수료 귀속을 승계월 기준 후임 설계사로 전환.
모집수수료는 원 모집설계사 귀속 유지(고아계약 승계 표준).

- DB V86: contract_succession 테이블 + 인덱스 + 메뉴/권한(GRP_PRD) + 공통코드 2그룹 + 테스트데이터 1건
- core: ContractSuccession VO/Resp/SaveReq/SearchParam + Mapper(.java/.xml)
  selectEffectiveSuccessions(settleMonth): 계약별 최근 ACTIVE 승계 1건 (DISTINCT ON)
- api: ContractSuccessionService/Controller (/api/contract-successions, CRUD+cancel)
- batch: CalcMaintainStep 이 effective 승계 사전로드(N+1 회피) 후 effectiveAgentId 결정,
  CommissionCalculator.calcMaintainLedger 오버로드로 후임 등급 payout + ledger agent_id 후임 기록.
  AggregateStep 은 ledger agent_id 집계라 무변경.
- frontend: api/succession.ts + ContractSuccessions.tsx + App.tsx 라우트

검증: 5모듈 compileJava SUCCESS / ga-frontend tsc 0 / Flyway v86 적용 /
  API CRUD+cancel+from==to 가드(E411) 라이브 PASS / resolver 쿼리 라이브 검증(계약1→후임 agent2).
배치 풀잡 e2e 는 정산월 원장 재생성(파괴적)이라 미실행.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ga-api/src/main/java/com/ga/api/controller/succession/ContractSuccessionController.java

@@ -0,0 +1,59 @@
+package com.ga.api.controller.succession;
+
+import com.ga.api.service.succession.ContractSuccessionService;
+import com.ga.common.annotation.DataChangeLog;
+import com.ga.common.annotation.RequirePermission;
+import com.ga.common.model.ApiResponse;
+import com.ga.common.model.PageResponse;
+import com.ga.core.vo.succession.ContractSuccessionResp;
+import com.ga.core.vo.succession.ContractSuccessionSaveReq;
+import com.ga.core.vo.succession.ContractSuccessionSearchParam;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import jakarta.validation.Valid;
+import lombok.RequiredArgsConstructor;
+import org.springframework.web.bind.annotation.*;
+
+@Tag(name = "계약 승계")
+@RestController
+@RequestMapping("/api/contract-successions")
+@RequiredArgsConstructor
+public class ContractSuccessionController {
+
+    private final ContractSuccessionService service;
+
+    @GetMapping
+    @RequirePermission(menu = "CONTRACT_SUCCESSION", perm = "READ")
+    public ApiResponse<PageResponse<ContractSuccessionResp>> list(
+            @ModelAttribute ContractSuccessionSearchParam param) {
+        return ApiResponse.ok(service.list(param));
+    }
+
+    @GetMapping("/{successionId}")
+    @RequirePermission(menu = "CONTRACT_SUCCESSION", perm = "READ")
+    public ApiResponse<ContractSuccessionResp> detail(@PathVariable Long successionId) {
+        return ApiResponse.ok(service.detail(successionId));
+    }
+
+    @PostMapping
+    @RequirePermission(menu = "CONTRACT_SUCCESSION", perm = "CREATE")
+    @DataChangeLog(menu = "CONTRACT_SUCCESSION", table = "contract_succession")
+    public ApiResponse<Long> create(@Valid @RequestBody ContractSuccessionSaveReq req) {
+        return ApiResponse.ok(service.create(req));
+    }
+
+    @PostMapping("/{successionId}/cancel")
+    @RequirePermission(menu = "CONTRACT_SUCCESSION", perm = "UPDATE")
+    @DataChangeLog(menu = "CONTRACT_SUCCESSION", table = "contract_succession")
+    public ApiResponse<Void> cancel(@PathVariable Long successionId) {
+        service.cancel(successionId);
+        return ApiResponse.ok();
+    }
+
+    @DeleteMapping("/{successionId}")
+    @RequirePermission(menu = "CONTRACT_SUCCESSION", perm = "DELETE")
+    @DataChangeLog(menu = "CONTRACT_SUCCESSION", table = "contract_succession")
+    public ApiResponse<Void> delete(@PathVariable Long successionId) {
+        service.delete(successionId);
+        return ApiResponse.ok();
+    }
+}

ga-api/src/main/java/com/ga/api/service/succession/ContractSuccessionService.java

@@ -0,0 +1,65 @@
+package com.ga.api.service.succession;
+
+import com.ga.common.exception.BizException;
+import com.ga.common.exception.ErrorCode;
+import com.ga.common.model.PageResponse;
+import com.ga.common.util.SecurityUtil;
+import com.ga.core.mapper.succession.ContractSuccessionMapper;
+import com.ga.core.vo.succession.ContractSuccessionResp;
+import com.ga.core.vo.succession.ContractSuccessionSaveReq;
+import com.ga.core.vo.succession.ContractSuccessionSearchParam;
+import com.ga.core.vo.succession.ContractSuccessionVO;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+@Transactional(readOnly = true)
+public class ContractSuccessionService {
+
+    private final ContractSuccessionMapper mapper;
+
+    public PageResponse<ContractSuccessionResp> list(ContractSuccessionSearchParam param) {
+        param.startPage();
+        return PageResponse.of(mapper.selectList(param));
+    }
+
+    public ContractSuccessionResp detail(Long successionId) {
+        ContractSuccessionResp resp = mapper.selectById(successionId);
+        if (resp == null) throw new BizException(ErrorCode.NOT_FOUND);
+        return resp;
+    }
+
+    @Transactional
+    public Long create(ContractSuccessionSaveReq req) {
+        if (req.getFromAgentId().equals(req.getToAgentId())) {
+            throw new BizException(ErrorCode.INVALID_PARAMETER, "전임과 후임 설계사가 같을 수 없습니다");
+        }
+        ContractSuccessionVO vo = new ContractSuccessionVO();
+        vo.setContractId(req.getContractId());
+        vo.setFromAgentId(req.getFromAgentId());
+        vo.setToAgentId(req.getToAgentId());
+        vo.setSuccessionDate(req.getSuccessionDate());
+        vo.setReason(req.getReason());
+        vo.setMemo(req.getMemo());
+        vo.setCreatedBy(SecurityUtil.getCurrentUserId());
+        mapper.insert(vo);
+        return vo.getSuccessionId();
+    }
+
+    /** 승계 취소 — status=CANCELED. 이후 정산월부터 유지수수료는 다시 직전 귀속 설계사에게. */
+    @Transactional
+    public void cancel(Long successionId) {
+        ContractSuccessionResp existing = mapper.selectById(successionId);
+        if (existing == null) throw new BizException(ErrorCode.NOT_FOUND);
+        mapper.cancel(successionId, SecurityUtil.getCurrentUserId());
+    }
+
+    @Transactional
+    public void delete(Long successionId) {
+        ContractSuccessionResp existing = mapper.selectById(successionId);
+        if (existing == null) throw new BizException(ErrorCode.NOT_FOUND);
+        mapper.delete(successionId);
+    }
+}