refactor: 降级到 Prisma 6，移除 adapter 依赖

Prisma 6 内置 SQLite 引擎，无需 adapter、无需编译工具链，
与 no-whatever 项目保持一致的技术方案。

src/lib/prisma.ts

@@ -1,14 +1,11 @@
-import { PrismaClient } from "@/generated/prisma/client";
-import { PrismaLibSql } from "@prisma/adapter-libsql";
+import { PrismaClient } from "@prisma/client";
 
-const globalForPrisma = globalThis as unknown as { prisma: PrismaClient };
+const globalForPrisma = globalThis as unknown as {
+  prisma: PrismaClient | undefined;
+};
 
-function createClient() {
-  const url = process.env.DATABASE_URL ?? "file:./dev.db";
-  const adapter = new PrismaLibSql({ url });
-  return new PrismaClient({ adapter });
+export const prisma = globalForPrisma.prisma ?? new PrismaClient();
+
+if (process.env.NODE_ENV !== "production") {
+  globalForPrisma.prisma = prisma;
 }
-
-export const prisma = globalForPrisma.prisma || createClient();
-
-if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;