feat(payment): sync plans and add coins rules

plans.md

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+GET https://proapi.banlv-ai.com/api/payment/plans
+结果：
+status=200
+success=true
+plans 数量 8
+VIP 套餐 3 个
+credits 套餐 5 个
+snake_keys=[]，已经没有 plan_id / amount_cents 这种字段
+schema 校验通过：proapi_plans_camel_schema_ok true
+前端按这个结构用：
+type PaymentPlan = {
+  planId: string;
+  planName: string;
+  orderType: 'vip_monthly' | 'vip_quarterly' | 'vip_annual' | 'dol';
+  vipDays: number | null;
+  dolAmount: number | null;
+  creditBalance: number;
+  amountCents: number;
+  originalAmountCents: number | null;
+  dailyPriceCents: number | null;
+  currency: string;
+};
+分组：
+const plans = res.data.plans;
+
+const vipPlans = plans.filter(p => p.vipDays !== null);
+const creditPlans = plans.filter(p => p.dolAmount !== null);
+下单仍然传 planId：
+{
+  "planId": "vip_monthly",
+  "payChannel": "stripe",
+  "autoRenew": true
+}
+价格、币种全部以前端拿到的 amountCents / currency 展示，不要写死。当前我这边访问 pro 返回的是 JPY，这是 Cloudflare 根据访问 IP 判的国家币种。