feat(admin): add registration policy settings and disabled register state

packages/db/prisma/migrations/20260210200148_admin_registration_policy_setting/migration.sql

@@ -0,0 +1,9 @@
+-- CreateTable
+CREATE TABLE "system_setting" (
+    "key" TEXT NOT NULL,
+    "value" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "system_setting_pkey" PRIMARY KEY ("key")
+);

packages/db/prisma/schema.prisma

@@ -87,3 +87,12 @@ model Verification {
   @@index([identifier])
   @@map("verification")
 }
+
+model SystemSetting {
+  key       String   @id
+  value     String
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  @@map("system_setting")
+}