Optimize index.html for SEO

[brucx]

Updated index.html to improve SEO by adding meta tags (description, keywords), Open Graph, Twitter Cards, and JSON-LD structured data. Refactored the semantic structure to use a single H1 for the main value proposition and adjusted CSS accordingly. Added a canonical link to https://runclawd.sh.

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PR created automatically by Jules for task 12524575277375678909 started by @brucx

[cloudflare-workers-and-pages]

Deploying runclawd with    Cloudflare Pages

Latest commit:	f15d3fe
Status:	✅  Deploy successful!
Preview URL:	https://f6a6e758.runclawd.pages.dev
Branch Preview URL:	https://seo-optimization-12524575277.runclawd.pages.dev

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[brucx]

H2 Check
Missing H2 tags can disrupt content hierarchy and SEO effectiveness.

Meta Description Check
SEO meta descriptions should be 140-160 characters to ensure full display and boost clicks.

[google-labs-jules]

H2 Check
Missing H2 tags can disrupt content hierarchy and SEO effectiveness.

Meta Description Check
SEO meta descriptions should be 140-160 characters to ensure full display and boost clicks.

Updated index.html to address feedback:

1. Promoted "Install" and "Device Approval" section titles from h3 to h2 to improve hierarchy.
2. Added a visually hidden <h2>Features</h2> to the features section for semantic structure without altering the visual design.
3. Shortened the meta description to 149 characters to fit within the recommended 140-160 range.