Fix broken and outdated links in web and demo workflows (#4071)

[Labreo]

Description

Addresses part of #4071 by updating broken and outdated documentation links across web and demo workflows:

• book_source/02_demos_tutorials_workflows/03_web_workflow.Rmd:
  • Upgraded Ameriflux and FLUXNET site list URLs to HTTPS and current paths.
  • Updated config.php repository link to the canonical develop branch.
• book_source/02_demos_tutorials_workflows/04_more_web_interface/02_hidden_analyses.Rmd:
  • Replaced defunct PalEON state data assimilation wiki URL with its Internet Archive snapshot.
• book_source/02_demos_tutorials_workflows/05_developer_workflows/04_docker/08_pecan_api.Rmd:
  • Pinned pecanapi package vignette link to release tag v1.7.1 where the vignette remains available.
• Updated CHANGELOG.md.

Motivation and Context

Addresses part of #4071.

Issue #4071 tracks broken documentation links across the repository. Fixing these links in modular pull requests keeps review cycles small and maintains documentation accuracy.

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I agree that PEcAn Project may distribute my contribution under any or all of
  • the same license as the existing code,
  • and/or the BSD 3-clause license.
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Labreo]

Updated according to suggestions and resolved the merge conflicts.