feat: 渠道展示、订阅套餐、系统配置全功能

- 新增 Channel / SubscriptionPlan / SystemConfig 三个数据模型
- Order 模型扩展支持订阅订单（order_type, plan_id, subscription_group_id）
- Sub2API client 新增分组查询、订阅分配/续期、用户订阅查询
- 订单服务支持订阅履约流程（CAS 锁 + 分组消失安全处理）
- 管理后台：渠道管理、订阅套餐管理、系统配置、Sub2API 分组同步
- 用户页面：双 Tab UI（按量付费/包月订阅）、渠道卡片、充值弹窗、订阅确认
- PaymentForm 支持 fixedAmount 固定金额模式
- 订单状态 API 返回 failedReason 用于订阅异常展示
- 数据库迁移脚本

src/app/api/admin/subscription-plans/[id]/route.ts

@@ -0,0 +1,90 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { verifyAdminToken, unauthorizedResponse } from '@/lib/admin-auth';
+import { prisma } from '@/lib/db';
+
+export async function PUT(request: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  if (!(await verifyAdminToken(request))) return unauthorizedResponse(request);
+
+  try {
+    const { id } = await params;
+    const body = await request.json();
+
+    const existing = await prisma.subscriptionPlan.findUnique({ where: { id } });
+    if (!existing) {
+      return NextResponse.json({ error: '订阅套餐不存在' }, { status: 404 });
+    }
+
+    // 如果更新了 group_id，检查唯一性
+    if (body.group_id !== undefined && Number(body.group_id) !== existing.groupId) {
+      const conflict = await prisma.subscriptionPlan.findUnique({
+        where: { groupId: Number(body.group_id) },
+      });
+      if (conflict) {
+        return NextResponse.json(
+          { error: `分组 ID ${body.group_id} 已被套餐「${conflict.name}」使用` },
+          { status: 409 },
+        );
+      }
+    }
+
+    const data: Record<string, unknown> = {};
+    if (body.group_id !== undefined) data.groupId = Number(body.group_id);
+    if (body.name !== undefined) data.name = body.name;
+    if (body.description !== undefined) data.description = body.description;
+    if (body.price !== undefined) data.price = body.price;
+    if (body.original_price !== undefined) data.originalPrice = body.original_price;
+    if (body.validity_days !== undefined) data.validityDays = body.validity_days;
+    if (body.features !== undefined) data.features = body.features;
+    if (body.for_sale !== undefined) data.forSale = body.for_sale;
+    if (body.sort_order !== undefined) data.sortOrder = body.sort_order;
+
+    const plan = await prisma.subscriptionPlan.update({
+      where: { id },
+      data,
+    });
+
+    return NextResponse.json({
+      ...plan,
+      price: Number(plan.price),
+      originalPrice: plan.originalPrice ? Number(plan.originalPrice) : null,
+    });
+  } catch (error) {
+    console.error('Failed to update subscription plan:', error);
+    return NextResponse.json({ error: '更新订阅套餐失败' }, { status: 500 });
+  }
+}
+
+export async function DELETE(request: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  if (!(await verifyAdminToken(request))) return unauthorizedResponse(request);
+
+  try {
+    const { id } = await params;
+
+    const existing = await prisma.subscriptionPlan.findUnique({ where: { id } });
+    if (!existing) {
+      return NextResponse.json({ error: '订阅套餐不存在' }, { status: 404 });
+    }
+
+    // 检查是否有活跃订单引用此套餐
+    const activeOrderCount = await prisma.order.count({
+      where: {
+        planId: id,
+        status: { in: ['PENDING', 'PAID', 'RECHARGING'] },
+      },
+    });
+
+    if (activeOrderCount > 0) {
+      return NextResponse.json(
+        { error: `该套餐仍有 ${activeOrderCount} 个活跃订单，无法删除` },
+        { status: 409 },
+      );
+    }
+
+    await prisma.subscriptionPlan.delete({ where: { id } });
+
+    return NextResponse.json({ success: true });
+  } catch (error) {
+    console.error('Failed to delete subscription plan:', error);
+    return NextResponse.json({ error: '删除订阅套餐失败' }, { status: 500 });
+  }
+}