refactor(b09): 라우터 쪼개기 — 산출 조건 문(GET/PUT /estimation/factors)을 Router_Factors 로 · Router.py 842 → 537줄

- get_bill · _project_root_of · _build_for 는 Router.py 에 그대로(랩탑_메인 CostSheet import 그대로)
- 새 파일은 본 라우터의 _project_root_of·_build_for 를 부를 때마다 빌려 씀 — 시험이 본 라우터 것을 바꿔 끼움
- 검증: 시험 1666 통과 · 골든셋 초록 · 재시작 뒤 B09 문 열하나(factors·base-data·price-sources·basis-sheet·machine-expense·
  design-doc-index·bill·unit-prices·edits·cost-sheet·PUT factors) 전부 200

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016VBGFXB9AbJBwXP19z75Qq

main.py

@@ -67,6 +67,7 @@ from B08_Quantity.B08_Quantity_Router_StructureSheet import router as b08_struct
 from B09_Estimation.B09_Estimation_Router import router as b09_estimation_router
 from B09_Estimation.B09_Estimation_Router_CostSheet import router as b09_cost_sheet_router
 from B09_Estimation.B09_Estimation_Router_Edits import router as b09_edits_router
+from B09_Estimation.B09_Estimation_Router_Factors import router as b09_factors_router
 from common_util.common_util_audit import note_api_call, record_call_burst
 from common_util.common_util_auth import (
     require_company,
@@ -640,6 +641,7 @@ app.include_router(b08_structure_sheet_router, dependencies=protected_with_compa
 app.include_router(b09_estimation_router, dependencies=protected_with_company)
 app.include_router(b09_cost_sheet_router, dependencies=protected_with_company)
 app.include_router(b09_edits_router, dependencies=protected_with_company)
+app.include_router(b09_factors_router, dependencies=protected_with_company)
 # 개발 전용 잠금 해제 — 다른 라우터와 **같은 보호**를 받는다(로그인·회사·프로젝트 접근).
 # 그 위에 서버가 환경까지 한 번 더 본다.
 app.include_router(dev_unlock_router, dependencies=protected_with_company)