feat: Phase 8 SaaS 확장 - 구독관리/결제내역 API 추가

- 사용량 조회 API (GET /subscriptions/usage)
- 데이터 내보내기 API (POST/GET /subscriptions/export)
- 결제 명세서 API (GET /payments/{id}/statement)
- DataExport 모델 및 마이그레이션 추가

LOGICAL_RELATIONSHIPS.md

@@ -1,6 +1,6 @@
 # 논리적 데이터베이스 관계 문서
 
-> **자동 생성**: 2025-12-19 16:12:19
+> **자동 생성**: 2025-12-19 16:48:57
 > **소스**: Eloquent 모델 관계 분석
 
 ## 📊 모델별 관계 현황
@@ -368,6 +368,34 @@ ### quotes
 - **items()**: hasMany → `quote_items`
 - **revisions()**: hasMany → `quote_revisions`
 
+### quote_formulas
+**모델**: `App\Models\Quote\QuoteFormula`
+
+- **category()**: belongsTo → `quote_formula_categories`
+- **ranges()**: hasMany → `quote_formula_ranges`
+- **mappings()**: hasMany → `quote_formula_mappings`
+- **items()**: hasMany → `quote_formula_items`
+
+### quote_formula_categorys
+**모델**: `App\Models\Quote\QuoteFormulaCategory`
+
+- **formulas()**: hasMany → `quote_formulas`
+
+### quote_formula_items
+**모델**: `App\Models\Quote\QuoteFormulaItem`
+
+- **formula()**: belongsTo → `quote_formulas`
+
+### quote_formula_mappings
+**모델**: `App\Models\Quote\QuoteFormulaMapping`
+
+- **formula()**: belongsTo → `quote_formulas`
+
+### quote_formula_ranges
+**모델**: `App\Models\Quote\QuoteFormulaRange`
+
+- **formula()**: belongsTo → `quote_formulas`
+
 ### quote_items
 **모델**: `App\Models\Quote\QuoteItem`
 
@@ -439,6 +467,12 @@ ### cards
 - **creator()**: belongsTo → `users`
 - **updater()**: belongsTo → `users`
 
+### data_exports
+**모델**: `App\Models\Tenants\DataExport`
+
+- **tenant()**: belongsTo → `tenants`
+- **creator()**: belongsTo → `users`
+
 ### departments
 **모델**: `App\Models\Tenants\Department`