P8 平台轻量化改造 + SSG修复 + 编程导师 + 文档完善

- Prisma: Tool 模型加 affiliateLink；免费用户沙盒 10→5 次/日
- 后端: Tools API + /admin/tools CRUD 5 端点；Practices 完整模块
- 导航: 主菜单隐藏企业版/社区（URL 可访问）
- 首页: 重定位为 AI 工具指南；新增精选工具区块；Feature 重写
- 工具页: affiliateLink 绿色推荐 Badge
- SSG 修复: config.ts 构建时直连 localhost:4000，页面 108→127
- 沙盒: 新增编程导师场景（苏格拉底教学法）
- 练习系统: Practices 多场景练习（含结构化评分）
- 技能广场: 6 个付费 Skill（标题大师/回款助手等）
- 管理后台: Models/Posts/Practices CRUD 页面
- 文档: README + progress.md 全面更新；AGENTS.md 同步定位
- 清理: .env.example 移除；tsbuildinfo gitignore

backend/src/modules/sandbox/sandbox.service.ts

@@ -26,7 +26,7 @@ export class SandboxService {
 
     const convId = conversationId || randomUUID();
 
-    // 今日配额：按 conversationId 去重计数
+    // 配额检查：先用每日免费配额，再用购买的额外配额
     const today = new Date();
     today.setHours(0, 0, 0, 0);
     const existing = await this.prisma.sandboxSession.findUnique({
@@ -36,8 +36,16 @@ export class SandboxService {
       const todayCount = await this.prisma.sandboxSession.count({
         where: { userId, createdAt: { gte: today } },
       });
-      if (todayCount >= (user.sandboxDaily || 10)) {
-        throw new HttpException('今日沙箱使用次数已用完', HttpStatus.TOO_MANY_REQUESTS);
+      const dailyLimit = user.sandboxDaily || 10;
+      if (todayCount >= dailyLimit) {
+        if ((user.sandboxExtra || 0) > 0) {
+          await this.prisma.user.update({
+            where: { id: userId },
+            data: { sandboxExtra: { decrement: 1 } },
+          });
+        } else {
+          throw new HttpException('今日沙箱使用次数已用完', HttpStatus.TOO_MANY_REQUESTS);
+        }
       }
     }
 
@@ -104,9 +112,17 @@ export class SandboxService {
       const todayCount = await this.prisma.sandboxSession.count({
         where: { userId, createdAt: { gte: today } },
       });
-      if (todayCount >= (user.sandboxDaily || 10)) {
-        yield JSON.stringify({ type: 'error', message: '今日沙箱使用次数已用完' } as StreamResult);
-        return;
+      const dailyLimit = user.sandboxDaily || 10;
+      if (todayCount >= dailyLimit) {
+        if ((user.sandboxExtra || 0) > 0) {
+          await this.prisma.user.update({
+            where: { id: userId },
+            data: { sandboxExtra: { decrement: 1 } },
+          });
+        } else {
+          yield JSON.stringify({ type: 'error', message: '今日沙箱使用次数已用完' } as StreamResult);
+          return;
+        }
       }
     }
 
@@ -259,7 +275,17 @@ export class SandboxService {
     const used = await this.prisma.sandboxSession.count({
       where: { userId, createdAt: { gte: today } },
     });
-    return { dailyLimit: user?.sandboxDaily || 10, used, remaining: (user?.sandboxDaily || 10) - used };
+    const dailyLimit = user?.sandboxDaily || 10;
+    const extra = user?.sandboxExtra || 0;
+    const dailyRemaining = Math.max(0, dailyLimit - used);
+    return {
+      dailyLimit,
+      used,
+      dailyRemaining,
+      extra,
+      canUse: dailyRemaining > 0 || extra > 0,
+      totalRemaining: dailyRemaining + extra,
+    };
   }
 
   async generateShareToken(userId: number, sessionId: number) {