Add NGU support, repo briefs, and CI security workflows

[michaelzick]

Summary

• Added canonical agent briefing files and repo-local skills for coding standards and syncing AGENTS.md to CLAUDE.md and GEMINI.md.
• Added CI and security automation for npm-based validation, brief drift checks, dependency auditing, secret scanning, dependency review, and CodeQL.
• Expanded the site with Nice Guy University flows, reCAPTCHA-backed contact and coupon forms, questionnaire and blog updates, shared analytics/navigation improvements, and refreshed SEO/sitemap assets.
• Updated server helpers, client recaptcha loading, Playwright coverage, and supporting test fixtures/types to match the new public surfaces.

Testing

• npm run agent-briefs:check
• npm run check
• Added and updated unit, sitemap, and Playwright E2E coverage for the new forms, promo flow, and mobile UI behavior.

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