Harden Next/OpenNext prefetch and prevent runaway _rsc requests

[meathill]

Background

freeaiapi hit a Next 16.3 + OpenNext _rsc prefetch loop (~10M Worker requests / 2 days). optimisticRouting: false did not fix it; disabling OpenNext cache interception did. This repo's apps/web uses Next + OpenNext.

Tasks

• Next.js is already 16.3.3+; keep related @next/* packages aligned.
• Keep enableCacheInterception disabled; if enabled, set it to false.
• Reduce unnecessary <Link> prefetch, especially footer / secondary / low-intent links (prefetch={false}).
• Verify production _rsc requests stop after the initial prefetch burst.
• Check Cloudflare Worker request metrics after deployment.

Upstream: opennextjs/opennextjs-cloudflare#1348 · opennextjs/opennextjs-aws#1212

[meathill]

已处理并上线待验证（commit 4fade34）：

• next / @next/third-parties 16.3.3→16.3.4，@opennextjs/cloudflare 1.20.4→1.20.6，wrangler 4.125→4.129
• wrangler.jsonc 中 observability.enabled 设为 false（字段保留），停止日志额度消耗
• open-next.config.ts 显式 enableCacheInterception: false（上游 opennextjs-cloudflare#1348 未合并前保持关闭）
• 全部 6 处 <Link> 加 prefetch={false}（header Logo、footer、ToolCard、RelatedTools、ConversionLinks、pdf-editor CTA）

本地验证：typecheck 通过、vitest 546 用例全过、next build 成功。生产 _rsc / Worker 请求量待部署后观察。