Switch from netlify link checker to lychee

[stefanv]

The netlify link checker hasn't been updated in years, and is now failing because of some outdated JS dependency.

[netlify]

❌ Deploy Preview for scientific-python-org failed.

Built without sensitive environment variables

Name	Link
🔨 Latest commit	68ef1d5
🔍 Latest deploy log	https://app.netlify.com/projects/scientific-python-org/deploys/6a10dacfb7ebe700089106aa

[bsipocz]

Copying the build issues from the build log here:

Issues found in 14 inputs. Find details below.
12:48:43 AM: [public/specs/core-projects/networkx/index.html]:
12:48:43 AM:    [404] https://networkx.org/documentation/stable/license.html (at 142:34) | Rejected status code: 404 Not Found
12:48:43 AM: [public/specs/spec-0003/index.html]:
12:48:43 AM:    [404] https://www.cdc.gov/ncbddd/disabilityandhealth/infographic-disability-impacts-all.html (at 154:123) | Rejected status code: 404 Not Found
12:48:43 AM: [public/specs/spec-0004/index.html]:
12:48:43 AM:    [403] https://anaconda.org/ (at 273:21) | Rejected status code: 403 Forbidden
12:48:43 AM:    [404] https://anaconda.org/%5Buser%5D/settings/access (at 278:10) | Rejected status code: 404 Not Found
12:48:43 AM: [public/specs/spec-0009/index.html]:
12:48:43 AM:    [403] https://medium.com/the-node-js-collection/healthy-open-source-967fa8be7951 (at 285:61) | Rejected status code: 403 Forbidden
12:48:43 AM:    [404] https://www.theopensourceway.org/the_open_source_way-guidebook-2.0.html#_project_and_community_governance (at 406:23) | Rejected status code: 404 Not Found
12:48:43 AM: [public/summits/developer/2023/general-planning/index.html]:
12:48:43 AM:    [403] [https://www.timeanddate.com/worldclock/converter.html?iso=20230227T170000&p1=224](https://www.timeanddate.com/worldclock/converter.html?iso=20230227T170000&p1=224) (at 135:28) | Rejected status code: 403 Forbidden
12:48:43 AM: [public/summits/developer/2023/index.html]:
12:48:43 AM:    [403] https://hackmd.io/@scientific-python/r1sq5vNHn (at 135:32) | Rejected status code: 403 Forbidden
12:48:43 AM: [public/summits/developer/2025-nov/index.html]:
12:48:43 AM:    [429] https://upload.wikimedia.org/wikipedia/commons/c/c7/ESS_logotype_cyan_S.png (at 141:11) | Rejected status code: 429 Too Many Requests
12:48:43 AM: [public/summits/developer/2025/index.html]:
12:48:43 AM:    [429] https://upload.wikimedia.org/wikipedia/commons/thumb/5/56/NSF_logo.svg/1280px-NSF_logo.svg.png (at 141:11) | Rejected status code: 429 Too Many Requests
12:48:43 AM: [public/summits/domain-stacks/index.html]:
12:48:43 AM:    [404] https://pangeo.io/packages.html (at 132:17) | Rejected status code: 404 Not Found
12:48:43 AM: [public/summits/domain-stacks/meeting1/index.html]:
12:48:43 AM:    [404] https://deploy-preview-286--scientific-python-org.netlify.app/software/ (at 176:14) | Rejected status code: 404 Not Found
12:48:43 AM: [public/summits/sparse/array-followup-2023-06-17/index.html]:
12:48:43 AM:    [403] https://hackmd.io/iEtdfbxfSbGwOAJTXmqyIQ (at 153:37) | Rejected status code: 403 Forbidden
12:48:43 AM: [public/summits/sparse/meeting1/index.html]:
12:48:43 AM:    [403] [https://www.timeanddate.com/worldclock/converter.html?iso=20220926T180000&p1=224](https://www.timeanddate.com/worldclock/converter.html?iso=20220926T180000&p1=224) (at 130:28) | Rejected status code: 403 Forbidden
12:48:43 AM: [public/summits/sparse/meeting2/index.html]:
12:48:43 AM:    [403] [https://www.timeanddate.com/worldclock/converter.html?iso=20230427T180000&p1=224](https://www.timeanddate.com/worldclock/converter.html?iso=20230427T180000&p1=224) (at 133:30) | Rejected status code: 403 Forbidden
12:48:43 AM: [public/tools/index.html]:
12:48:43 AM:  [ERROR] file:///opt/build/repo/public/tools/pydata-sphinx-theme.readthedocs.io (at 149:92) | File not found. Check if file exists and path is correct
12:48:43 AM:    [404] https://scientific-python.org/calendar (at 187:45) | Rejected status code: 404 Not Found
12:48:43 AM: 🔍 4059 Total (in 1m 51s 654ms) 🔗 952 Unique ✅ 3924 OK 🚫 17 Errors 👻 112 Excluded ⛔ 6 Unsupported 🔀 40 Redirects
12:48:43 AM: Hint: Encountered rate limit responses. You might be able to work around this by adding `[hosts."upload.wikimedia.org"]` to the TOML config to adjust the `concurrency` and `request_interval` values.
12:48:43 AM: Hint: Followed 40 redirects. You might want to consider replacing redirecting URLs with the resolved URLs. Use verbose mode (`-v`/`-vv`) to see redirection details.
12:48:43 AM: Hint: You can configure accepted/rejected response codes with `-a` or `--accept`
12:48:45 AM: Failed during stage 'building site': Build script returned non-zero exit code: 2 (https://ntl.fyi/exit-code-2)

[stefanv]

I love how these failed links were simply not found before 👀