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/core/src/usage.ts

@@ -0,0 +1,64 @@
+/**
+ * 用量聚合辅助（公共约定 §5：后端换算、微分取整、聚合先求和再一次取整）
+ */
+import {
+  microSumToUsdStr,
+  qpuAt,
+  quotaToMicroUsd,
+  quotaToUsdStr,
+} from "./money.ts";
+
+/** 上游事实：QuotaPerUnit 默认 500000（qpu_history 未采样时的回退） */
+export const DEFAULT_QPU = 500_000;
+
+export type QpuPoint = { qpu: number; effective_from: Date | number };
+
+export function resolveQpuTimeline(
+  rows: readonly QpuPoint[],
+): QpuPoint[] {
+  if (rows.length > 0) return [...rows];
+  return [{ qpu: DEFAULT_QPU, effective_from: 0 }];
+}
+
+export interface UsageSum {
+  count: number;
+  quota: number;
+  quota_usd: string;
+}
+
+export function emptyUsage(): UsageSum {
+  return { count: 0, quota: 0, quota_usd: "0.00" };
+}
+
+/** 逐行微分累加（历史正确性：按日志时刻取 QPU） */
+export function sumUsage(
+  rows: ReadonlyArray<{ quota: number; created_at: Date | number }>,
+  timeline: readonly QpuPoint[],
+): UsageSum {
+  let quota = 0;
+  let micro = 0;
+  for (const r of rows) {
+    quota += r.quota;
+    const qpu = qpuAt(r.created_at, timeline);
+    micro += quotaToMicroUsd(r.quota, qpu);
+  }
+  return { count: rows.length, quota, quota_usd: microSumToUsdStr(micro) };
+}
+
+export function usageAt(
+  quota: number,
+  created_at: Date | number,
+  timeline: readonly QpuPoint[],
+): UsageSum {
+  const qpu = qpuAt(created_at, timeline);
+  return { count: 1, quota, quota_usd: quotaToUsdStr(quota, qpu) };
+}
+
+export function addUsage(a: UsageSum, b: UsageSum): UsageSum {
+  // 合并已成形的两段时，quota_usd 需重算——调用方应尽量走 sumUsage
+  return {
+    count: a.count + b.count,
+    quota: a.quota + b.quota,
+    quota_usd: a.quota_usd,
+  };
+}