Accessibility: Added missing labels to webhook details and headers

[andreaslborg]

Description

Found missing label attributes on UUI controls in the webhook workspace causing accessibility console warnings.

UUI-INPUT needs a `label`
UUI-TOGGLE needs a `label`
UUI-BUTTON needs a `label`

Changes:

• webhook-details-workspace-view.element.ts added webhooks_url label to uui-input, and the webhooks_enabled to uui-toggle, so accessible names are concise and match what the controls represent.

• input-webhook-headers.element.ts added a localized label attribute to the "Add" uui-button (general_add) and replaced the hardcoded "Add" text with <umb-localize key="general_add">.

Testing

1. Open the Webhooks section and create or edit a webhook.
2. Open browser console: verify no needs a 'label' accessibility warnings appear for the URL input, the enabled toggle, or the Add headers button.
3. Add a header and verify the "Add" button still functions correctly and displays the localized text.

[github-actions]

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[andreaslborg]

Hi @AndyButland, should this also target v17/dev or is it fine as it?

[AndyButland]

It's OK as is. We can cherry-pick it over. For future PRs though, I'd suggest targeting v17/dev if it's any sort of bug fix, accessibility improvement etc., as we'd want that in the LTS. main would be for 18+, so really only medium sized new features and of course anything that builds on an 18 only feature/

[AndyButland]

Thanks @andreaslborg. Spotted one visual issue with this update - can you see what you think please?

[AndyButland]

Thanks @andreaslborg - all looks good now.