feat: add llms.txt for AI discoverability

[jonathimer]

Summary

• Add llms.txt file to /public/ directory for AI system discoverability
• Helps ChatGPT, Claude, Perplexity, and other AI systems understand site structure
• Improves AI citability and accurate referencing of LFX Insights content

Test plan

• Verify file is accessible at https://insights.lfx.org/llms.txt after deployment
• Content renders as plain text

[Copilot]

Pull request overview

Adds an llms.txt file under frontend/public/ so it will be served at /llms.txt and can be used by LLM-based tools to understand and cite the LFX Insights site.

Changes:

• Add frontend/public/llms.txt describing LFX Insights, key pages, features, and contact links.

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[Copilot]

/project/[slug] looks like a Nuxt/Next-style file-system route placeholder, but the actual public URL pattern in this repo is /project/:slug (e.g., links/sitemap/stress scripts use /project/${slug}). As written, /project/[slug] would be a literal path that 404s and may mislead AI consumers; please update the entry to the real URL pattern (e.g., /project/{slug}) and consider listing the key project subpages if relevant (security, contributors, etc.).

Suggested change

	- /project/[slug]: Individual project dashboards with development, contributor, security, and popularity metrics
	- /project/{slug}: Individual project dashboards with development, contributor, security, and popularity metrics