v1.2.0: Security hardening, frontmatter fix, install improvements

Add demo section and link to YouTube

Remove demo section from README

add: YouTube demo video to README

Update README.md

update: README with cover image and demo GIFs

add: cover image and demo GIFs for GitHub README

update: performance agent with Lighthouse 13.0, CrUX Vis, FID cleanup

enhance: programmatic SEO with scaled abuse enforcement context

update: industry templates with GEO, ecommerce schema, GBP 2025, SaaS comparisons

enhance: schema templates with ProductGroup, ProfilePage, Certification

enhance: image SEO with fetchpriority, picture element, JPEG XL, decoding

update: technical SEO with AI crawlers, JS canonical guidance, mobile-first note

update: content quality with HCU merger, word count context, Flesch note, AI Mode

update: CWV references with FID Sept 2024 removal, Lighthouse 13.0, mobile-first completion