Implement llms.txt specification and differentiate from llm.txt

The current llm.txt file in @apps/portal/llm.txt is intended to provide information for Large Language Models (LLMs) but is currently just a list of URLs. This does not conform to the emerging llms.txt specification https://llmstxt.org/, which defines a structured Markdown file for LLM content indexing.

This ticket aims to correctly implement the llms.txt specification for the Neo.mjs website and clarify its purpose in relation to a potential llm.txt for crawler permissions.

Acceptance Criteria:

1. Rename/Refactor llm.txt to llms.txt: The existing llm.txt in @apps/portal/llm.txt should be replaced or transformed into a new llms.txt file that adheres to the https://llmstxt.org/ specification.
2. Update generateSeoFiles.mjs: The buildScripts/generateSeoFiles.mjs script must be modified to generate the new llms.txt file.
3. llms.txt Content Structure: The generated llms.txt must:
   • Be a Markdown document.
   • Include a mandatory H1 header for the project/site name (e.g., # Neo.mjs Platform).
   • Contain an optional blockquote for a concise summary of the website.
   • Feature additional Markdown sections for detailed information.
   • Include H2-delimited "file lists" with URLs pointing to more detailed Markdown versions of relevant pages (e.g., key guides, API documentation).
4. Content Generation Strategy: Define and implement a strategy for populating the llms.txt content. This could involve:
   • Automatically extracting summaries from existing Markdown files.
   • Allowing for manual curation of key summaries and links.
   • Leveraging the learn/tree.json structure to identify important content.
5. Differentiation: Clarify the role of llm.txt (for crawler permissions) versus llms.txt (for content indexing). If a separate llm.txt for permissions is deemed necessary and distinct from robots.txt, a plan for its generation should be included. For now, the primary focus is on llms.txt.