feat(core,db): 业务核心与数据访问层

core：DTO/错误信封/时间口径/微分折算/dedupe_key/加密与 PBKDF2/契约 zod/logtape/上游客户端。
db：八表 Drizzle schema + 仓储 + drizzle 配置。

packages/db/src/index.ts

@@ -0,0 +1,13 @@
+import { drizzle } from "drizzle-orm/postgres-js";
+import postgres from "postgres";
+import * as schema from "./schema.ts";
+
+export function createDb(connectionString: string) {
+  const client = postgres(connectionString, { max: 10 });
+  return drizzle(client, { schema });
+}
+
+export type Db = ReturnType<typeof createDb>;
+
+export * from "./schema.ts";
+export * from "./repos.ts";