refactor: 替换 better-sqlite3 为 libsql 适配器

移除 C++ 原生依赖，Dockerfile 不再需要 python3/make/g++，
构建更快、镜像更轻。

src/lib/prisma.ts

@@ -1,11 +1,11 @@
 import { PrismaClient } from "@/generated/prisma/client";
-import { PrismaBetterSqlite3 } from "@prisma/adapter-better-sqlite3";
+import { PrismaLibSql } from "@prisma/adapter-libsql";
 
 const globalForPrisma = globalThis as unknown as { prisma: PrismaClient };
 
 function createClient() {
   const url = process.env.DATABASE_URL ?? "file:./dev.db";
-  const adapter = new PrismaBetterSqlite3({ url });
+  const adapter = new PrismaLibSql({ url });
   return new PrismaClient({ adapter });
 }