chore: 初始化仓库

中华文明全图鉴——文物全图系统（PC Web 地图 + NestJS API + 管理后台）。
含三大 IP（文物南迁北归 / 国宝海外回归 / 博物馆手艺人）、AI 文物对话、
文物地图与详情、以及 demo-video-kit 演示视频生成工具。

apps/api/src/common/rate-limit.guard.ts

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+import {
+  CanActivate,
+  ExecutionContext,
+  HttpException,
+  HttpStatus,
+  Injectable,
+} from "@nestjs/common";
+import { Request } from "express";
+
+/**
+ * 简单的内存级 IP 限流守卫：滑动窗口。
+ * 用于保护成本敏感的 AI 接口，防止被刷爆额度。
+ */
+@Injectable()
+export class RateLimitGuard implements CanActivate {
+  private static readonly WINDOW_MS = 60_000;
+  private static readonly MAX_REQUESTS = 20;
+  private static readonly buckets = new Map<string, number[]>();
+
+  canActivate(context: ExecutionContext): boolean {
+    const req = context.switchToHttp().getRequest<Request>();
+    const forwarded = req.headers["x-forwarded-for"];
+    const ip =
+      (Array.isArray(forwarded) ? forwarded[0] : forwarded?.split(",")[0])?.trim() ||
+      req.ip ||
+      "unknown";
+
+    const now = Date.now();
+    const recent = (RateLimitGuard.buckets.get(ip) ?? []).filter(
+      (t) => now - t < RateLimitGuard.WINDOW_MS
+    );
+
+    if (recent.length >= RateLimitGuard.MAX_REQUESTS) {
+      throw new HttpException(
+        "请求过于频繁，请稍后再试",
+        HttpStatus.TOO_MANY_REQUESTS
+      );
+    }
+
+    recent.push(now);
+    RateLimitGuard.buckets.set(ip, recent);
+    return true;
+  }
+}