Audit and defer third-party browser JavaScript

[davorg]

Problem

Several pages load third-party JavaScript that may delay parsing, add privacy/security exposure, or be unnecessary:

• Chart.js is loaded synchronously inside the person template.
• AddThis is loaded on every page.
• Bootstrap, analytics, Amazon Store, newsletter, and other widgets add further third-party dependencies.

Backend rendering is now much lighter, so browser-side dependencies are a likely next source of perceived latency.

Proposed investigation

• Measure representative pages with browser performance tooling.
• Confirm which integrations are still used and remove obsolete ones.
• Ensure page-specific libraries are only loaded where needed.
• Defer, asynchronously initialise, or self-host retained scripts where appropriate.
• Review Subresource Integrity and Content Security Policy implications.

Acceptance criteria

• There is a documented keep/remove decision for each third-party script.
• Chart.js no longer blocks HTML parsing on person pages.
• Obsolete global scripts are removed.
• Retained scripts fail without breaking core page content.
• Before/after performance measurements are recorded.