feat(#614): warn when using deprecated countdown-timer note appearance

[santhosh-7777]

Description

Adds a new form validation that warns when the deprecated countdown-timer
appearance is used on note fields for CHT versions >= 4.7.0.

#614

Code review items

• Readable: Follows existing validation patterns
• Documented: N/A
• Tested: Unit tests added in test/lib/validation/form/note-countdown-timer.spec.js
• Backwards compatible: Only warns for CHT >= 4.7.0, skips older versions

[santhosh-7777]

Hi @jkuester! I've implemented the form validation for issue #614.

The new note-countdown-timer.js validation:

• Skips validation for CHT versions < 4.7.0
• Finds body nodes with countdown-timer appearance
• Checks if the associated bind node has a readonly attribute
• Prints a warning if deprecated usage is found
  Unit tests are included. Please let me know if any changes are needed. Thanks!

[santhosh-7777]

Hi @jkuester , I’ve fixed the ESLint issues and pushed the updates.
All checks should pass once the workflows are approved.
Please let me know if anything else is needed !