feat(llms): list all docs pages in llms.txt and add a coverage check

[thzgajendra]

Description:

• Lists every docs page in public/llms.txt, which previously linked 66 of 105 pages.
• Fixes llms.txt is missing 30 of 76 docs pages, including the MCP and LLM guides #231.
• Why: llms.txt is the file AI tools read first. It omitted the MCP and LLM guides and all 18 production guides, so GoFr's AI features were invisible in its own AI index.

What changed in llms.txt:

• New AI and agents section at the top: MCP, LLM and streaming guides, each with a one-line description.
• New Production guides section with the 18 /docs/guides/* pages, each with a one-line description.
• Added to existing sections: 13 advanced-guide pages, Cloud SQL, Elasticsearch migrations, the four gofr CLI subcommand pages, the /comparison and /migrate indexes, the /docs home, and llms-full.txt.
• The MCP entry describes it as read-only (GET/HEAD/OPTIONS/QUERY) per the docs; it does not repeat the page's "validation" wording (see MCP docs page may overstate validation; verify and correct #236).

Not included: docs/quick-start/cli/page.md in gofr is an empty file, so it is not listed. It looks like a stray file and may be worth a separate look.

Breaking Changes (if applicable):

• None. Content-only change to a static file.

Additional Information:

• Coverage checked by comparing every non-empty page.md route in gofr-dev/gofr@development docs/ against the links in llms.txt: before, 39 of 105 pages were missing; after, all 105 are listed.
• All 113 unique URLs in the new llms.txt return HTTP 200 on https://gofr.dev (checked with curl).
• The issue counted 30 missing pages; the comparison found 9 more (injecting-databases-drivers, datasources/migrations/elasticsearch, four gofrcli pages, /comparison, /migrate, /docs) and these are included too.
• No dependencies added.
• Related: Add AI features (MCP, LLM) to AGENTS.md and README #232 (AGENTS.md/README), which lives in gofr-dev/gofr.