feat: 联盟返佣系统规范化并打通技能广场（无 ICP 证合规变现主路径）

- 新增 AffiliateProgram / AffiliateLink / AffiliateClick 规范化 Prisma 模型
  取代原手写裸表 affiliate_stats / affiliate_clicks
- 新增迁移 prisma/migrations/20260711000000_add_affiliate_models
- 重构 affiliate.service.ts 改用 Prisma ORM，消除 $queryRawUnsafe SQL 注入
- 重构 affiliate.controller.ts 接口：programs / links(?skillId,?toolId) / stats / click
- 前端 affiliate 页接入真实接口，移除硬编码 demo 数据
- 技能详情页新增「学此技能推荐使用的工具」联盟链接区块
- 新增 affiliate.service.spec.ts（4 用例通过）与幂等种子 seed-affiliate.ts
- 更新 docs/progress/current.md，明确无 ICP 经营许可证下以联盟返佣为合规变现主路径
- 含此前工作区未提交改动（工具 slug 路由、支付/订单、SEO 等）

Co-Authored-By: opencode <opencode@anthropic.com>

frontend/package-lock.json

@@ -30,6 +30,7 @@
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         "highlight.js": "^11.11.1",
         "lucide-react": "^1.14.0",
+        "marked": "^18.0.5",
         "next": "^14.2.35",
         "next-themes": "^0.4.6",
         "postcss": "^8.5.14",
@@ -8044,6 +8045,18 @@
         "@jridgewell/sourcemap-codec": "^1.5.5"
       }
     },
+    "node_modules/marked": {
+      "version": "18.0.5",
+      "resolved": "https://registry.npmmirror.com/marked/-/marked-18.0.5.tgz",
+      "integrity": "sha512-S6GcvALHg6K4ohtu4E7x0a1AqhAjp6cV8KhLSyN9qVapnzJkusVBxZRcIU9AeYsbe6P1hKDusSbEOzGyyuce6w==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/math-intrinsics": {
       "version": "1.1.0",
       "resolved": "https://registry.npmmirror.com/math-intrinsics/-/math-intrinsics-1.1.0.tgz",