fix(a11y): label evaluator select and notes textarea in invitation dialog

[anishkb-dev]

The evaluator dropdown and the notes textarea in the auditor invitation dialog are plain <select> and <textarea> elements. Each has a <label> rendered above it, but nothing connects the two, so screen readers announce both controls without a name.

Adds htmlFor to each label and a matching id to each control.

A note on scope: this started out much larger and covered the <Select> components in the New Evaluation wizard too. Those turned out not to need it — opub-ui's Select already calls useId() and passes the same id to both the <label htmlFor> it renders and the native <select>, so those controls are labelled correctly already and passing an explicit id only replaces the generated one. I dropped them rather than add lines that change nothing.

While checking that, I did find two things that look wrong but are separate from this: htmlFor="auditType" and htmlFor="auditScope" in EvaluationConfiguration.tsx point at ids that don't exist anywhere, and the <Label htmlFor="evaluator-technical"> in ModelSelectionModal.tsx is a heading for a radio group but targets the first radio, which gives that one button two labels. Happy to open an issue for those if useful.