feat: add admin authentication

apps/api/prisma/schema.prisma

@@ -138,6 +138,18 @@ model Tag {
   @@unique([brandId, name])
 }
 
+model AdminUser {
+  id           String   @id @default(uuid())
+  username     String   @unique
+  passwordHash String
+  displayName  String
+  role         String   @default("admin")
+  isEnabled    Boolean  @default(true)
+  lastLoginAt  DateTime?
+  createdAt    DateTime @default(now())
+  updatedAt    DateTime @updatedAt
+}
+
 model BookingTag {
   bookingId String
   tagId     String

apps/api/prisma/seed.ts

@@ -1,4 +1,5 @@
 import { PrismaClient } from "@prisma/client";
+import { hash } from "bcryptjs";
 
 const prisma = new PrismaClient();
 
@@ -54,6 +55,15 @@ async function main(): Promise<void> {
       create: { brandId: brand.id, name, isPreset: true },
     });
   }
+  await prisma.adminUser.upsert({
+    where: { username: "admin" },
+    update: {},
+    create: {
+      username: "admin",
+      passwordHash: await hash(process.env.SEED_ADMIN_PASSWORD ?? "change-me-now-123", 12),
+      displayName: "品牌管理员",
+    },
+  });
 }
 
 main().finally(() => prisma.$disconnect());