Add a concise privacy and data-use page for analytics, newsletter, and Ask Mantosh

Priority: High

Problem

The public site uses Plausible analytics, sends newsletter subscriptions to Buttondown, and sends Ask Mantosh questions to a Cloudflare Worker. These flows are privacy-conscious by design, but there is no concise public page that explains what data is sent, what is retained, which third parties are involved, and what a visitor should expect.

Goal

Add a plain-language privacy/data-use page that reflects the actual production implementation without legalistic boilerplate or unsupported promises.

Scope

• Document Plausible analytics behavior and what visitor data is or is not collected.
• Document newsletter signup data sent to Buttondown and the subscription/unsubscribe lifecycle.
• Document Ask Mantosh question processing, storage/retention boundaries, quotas/abuse controls, and third-party infrastructure.
• Document cookies/local storage used for appearance or conversation state where applicable.
• Link to relevant third-party policies only where useful.
• Add an easy-to-find footer or appropriate site-wide link.
• Keep the page synchronized with docs/SYSTEM_STATE.md and executable configuration.

Acceptance criteria

• A public privacy/data-use page exists and is linked from appropriate public surfaces.
• It accurately describes analytics, Buttondown, Ask Mantosh, local storage, and relevant third parties.
• It makes no claim that is broader than the deployed implementation can substantiate.
• Newsletter and Ask Mantosh behavior described on the page matches production.
• Documentation/audits are updated so material privacy-language drift is detectable where practical.

Start with docs/SYSTEM_STATE.md and the executable configuration, then trace the production analytics, newsletter, Ask Mantosh, local-storage, and site-link behavior. Create the public page and appropriate site-wide link, ensuring its statements match production and updating documentation or audits so material privacy-language drift is detectable.