Migrate `sw-field-copyable` to `mt-field-copyable` in the Administration

Sub-issue of #15461.

### Scope

Replace all remaining `` usages in the Administration with ``.

Usage at the time of writing: **5 occurrences in 5 files**

```bash
grep -rE '/]|$)' src/Administration/Resources/app/administration/src
```

### Acceptance criteria

- All in-scope `` tags are replaced by ``.
- No new usages of `sw-field-copyable` are introduced.
- Behaviour parity is maintained for props, emitted events and slot content.
- Unit/E2E tests are updated only where selectors or DOM structure changed.
- AC validation is based on component tags (`sw-field-copyable` -> `mt-field-copyable`), not on
internal Meteor DOM classes (e.g. `.mt-field-copyable`).
- Wrapper or deprecated fallback usage is not required for this component.

Run the provided grep command in src/Administration/Resources/app/administration/src to locate the five remaining component usages. Replace the tags while preserving props, emitted events, and slot content, then update tests only if selectors or DOM structure changed; done means no in-scope sw-field-copyable tags remain and validation checks component tags rather than internal Meteor classes.

Written by the indexing model from the issue text.