Validate and update links (STF-557)

[oschwald]

Validated every link in the repo with the lychee link checker and updated those that were stale or redirecting. Also adds a lychee config and a Links CI workflow (push, pull request, weekly schedule) so link rot is caught automatically going forward. max_redirects = 0 so any moved link is surfaced and updated to its canonical destination.

Final lychee result: 36 OK, 0 Errors, 2 Excluded.

Links updated (old -> new)

• https://www.maxmind.com/ -> https://www.maxmind.com/en/home (composer.json)
• https://dev.maxmind.com/geoip/docs/web-services -> https://dev.maxmind.com/geoip/docs/web-services/ (CLAUDE.md)
• https://dev.maxmind.com/geoip/docs/web-services?lang=en -> https://dev.maxmind.com/geoip/docs/web-services/?lang=en (README.md, src/Model/City.php, Country.php, Enterprise.php, Insights.php)
• https://dev.maxmind.com/geoip/docs/databases?lang=en -> https://dev.maxmind.com/geoip/docs/databases/?lang=en (README.md)
• https://dev.maxmind.com/geoip/updating-databases?lang=en -> https://dev.maxmind.com/geoip/updating-databases/?lang=en (README.md)
• https://php.net/manual/en/book.phar.php -> https://www.php.net/manual/en/book.phar.php (README.md)
• https://php.net/manual/en/book.curl.php -> https://www.php.net/manual/en/book.curl.php (README.md)
• https://www.maxmind.com/en/correction -> https://www.maxmind.com/en/geoip-data-correction-request (README.md)
• https://www.maxmind.com/en/support -> https://support.maxmind.com/knowledge-base (README.md, 2 occurrences)

Historical CHANGELOG.md entries are intentionally left unchanged (excluded via exclude_path).

Part of STF-557.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request configures the Lychee link checker by adding a lychee.toml configuration file, adding .lycheecache to .gitignore, and updating various documentation and source code URLs to their canonical, non-redirecting forms. The review feedback suggests a key improvement to the Lychee configuration: removing the 500..=599 status code range from the accepted list to ensure that persistent server errors are properly flagged rather than silently ignored.

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[gemini-code-assist]

Accepting all 500..=599 (Server Error) status codes will cause lychee to treat permanently broken links or down servers as successful, leading to silent failures. Since lychee has a built-in retry mechanism for transient errors, it is safer to remove "500..=599" from the accept list so that persistent server errors are properly surfaced.

Suggested change

	# 500-599: Server errors (temporary issues shouldn't fail CI)
	# 999: LinkedIn's custom status code
	accept = ["100..=103", "200..=299", "403", "429", "500..=599", "999"]
	# 999: LinkedIn's custom status code
	accept = ["100..=103", "200..=299", "403", "429", "999"]

[oschwald]

Keeping 500..=599 in accept, matching the dev-site and blog-site configs — transient upstream 5xx shouldn't fail link-checking CI.

— Claude (posted on Greg's behalf)