chore: update Node.js requirement to 24.20.0

[jbair06]

Fixes #3368

Updates the Node.js version requirement from 24.19.0 to 24.20.0 (latest LTS) in engines fields, Dockerfiles, and READMEs across front-end, back-end, and automation.

[swirlds-automation]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.98%. Comparing base (aeb3fe7) to head (ad48281).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3369   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         213      213           
  Lines        6699     6699           
  Branches     1237     1209   -28     
=======================================
  Hits         6698     6698           
  Misses          1        1           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.