feat: [demo-tenant] 프로모션 설정 기능 추가

- 생성 모달에 프로모션 섹션 추가 (개발비 할인/면제, 구독료 할인, 무료기간)
- Alpine.js 기반 슬라이더/토글 UI, 자동 비율 조절
- options JSON에 promotion 키로 프로모션 데이터 저장
- 상세 모달에 프로모션 조건 표시

app/Http/Controllers/Sales/DemoTenantController.php

@@ -145,6 +145,13 @@ public function store(Request $request)
             'email' => 'nullable|email|max:100',
             'duration_days' => 'required|integer|min:7|max:60',
             'preset' => 'nullable|string|in:manufacturing,none',
+            'promo_dev_type' => 'nullable|string|in:percent,amount',
+            'promo_dev_percent' => 'nullable|integer|min:0|max:50',
+            'promo_dev_amount' => 'nullable|integer|min:0|max:5000000',
+            'promo_dev_waive' => 'nullable|in:0,1',
+            'promo_sub_percent' => 'nullable|integer|min:0|max:50',
+            'promo_free_months' => 'nullable|integer|in:0,1,2,3,6',
+            'promo_note' => 'nullable|string|max:200',
         ]);
 
         $partner = SalesPartner::where('user_id', auth()->id())->first();
@@ -158,6 +165,21 @@ public function store(Request $request)
             'created_by_user_name' => auth()->user()->name ?? '',
         ];
 
+        // 프로모션 설정
+        if ($request->filled('promo_dev_type')) {
+            $options['promotion'] = [
+                'dev_discount_type' => $request->input('promo_dev_type'),
+                'dev_discount_percent' => (int) $request->input('promo_dev_percent', 0),
+                'dev_discount_amount' => (int) $request->input('promo_dev_amount', 0),
+                'dev_waive' => $request->input('promo_dev_waive') === '1',
+                'sub_discount_percent' => (int) $request->input('promo_sub_percent', 0),
+                'free_months' => (int) $request->input('promo_free_months', 0),
+                'note' => $request->input('promo_note', ''),
+                'applied_at' => now()->toDateTimeString(),
+                'applied_by_user_id' => auth()->id(),
+            ];
+        }
+
         $tenant = new Tenant;
         $tenant->forceFill([
             'company_name' => $request->input('company_name'),