Add SNS Marketing Campaign feature

- Add cash_cc_balance to User model (withdrawable CC)
- Create SnsShareSubmission model for SNS share verification
- Add marketing campaign settings to SystemSettings
- Add reward_type to ReferralReward model
- Create /api/sns-share endpoints for submission and verification
- Add referral signup reward logic (10CC on signup)
- Create /sns-share user page for SNS sharing
- Create /admin/sns-shares management page
- Add marketing settings UI to admin settings page
- Add SNS Shares menu to admin sidebar

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/schemas/settings.py

@@ -22,6 +22,16 @@ class SystemSettingsUpdate(BaseModel):
     referral_reward_percent: Optional[float] = None
     referral_reward_type: Optional[str] = None
 
+    # 마케팅 캠페인 설정
+    marketing_enabled: Optional[bool] = None
+    marketing_start_date: Optional[datetime] = None
+    marketing_end_date: Optional[datetime] = None
+    sns_share_reward_cc: Optional[float] = None
+    referral_signup_reward_cc: Optional[float] = None
+    event_cc_validity_months: Optional[int] = None
+    withdrawal_enabled: Optional[bool] = None
+    min_withdrawal_usd: Optional[float] = None
+
 
 class SystemSettingsResponse(BaseModel):
     """시스템 설정 응답 스키마"""
@@ -42,6 +52,17 @@ class SystemSettingsResponse(BaseModel):
     referral_reward_enabled: bool = True
     referral_reward_percent: float = 10.0
     referral_reward_type: str = "one_time"
+
+    # 마케팅 캠페인 설정
+    marketing_enabled: bool = False
+    marketing_start_date: Optional[datetime] = None
+    marketing_end_date: Optional[datetime] = None
+    sns_share_reward_cc: float = 3.0
+    referral_signup_reward_cc: float = 10.0
+    event_cc_validity_months: int = 6
+    withdrawal_enabled: bool = True
+    min_withdrawal_usd: float = 10.0
+
     created_at: Optional[datetime] = None
     updated_at: Optional[datetime] = None