Refactor: Enhance labelText to support VDOM and remove innerHTML usage

Refactor labelText config in CheckBox and TextField (and potentially other fields extending Field) to support Object (single VDOM node) and Object[] (array of VDOM nodes) in addition to String.

Crucially, this refactoring must remove the usage of .html (innerHTML) assignment in afterSetLabelText and replace it with a safer VDOM-based approach (setting .vdom or .cn and .text), similar to the recent valueLabel fix. This mitigates potential XSS vulnerabilities associated with innerHTML.

Scope:

• Update src/form/field/Base.mjs (if labelText is defined there) or Text.mjs, CheckBox.mjs, etc.
• Ensure afterSetLabelText handles String (as text), Object, and Object[].
• Verify backward compatibility for existing string-based labels (rendering as text, not HTML, unless we explicitly decide to keep HTML support for strings - decision needed: strictly text for strings like valueLabel, or keep HTML support for backward compat? -> Prompt implies "custom vdom definition (to close a XSS vulnerability)", suggesting strings should become text-only or we need a clear migration path).

Note: This does NOT involve renaming labelText to label, keeping the scope manageable while improving security and flexibility.