Migrate `sw-label` to `mt-label` in the Administration

Sub-issue of #15461.

### Scope

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

Usage at the time of writing: **63 occurrences in 36 files**

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

### Acceptance criteria

- All in-scope `` tags are replaced by ``.
- No new usages of `sw-label` 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-label` -> `mt-label`), not on
internal Meteor DOM classes (e.g. `.mt-label`).
- Wrapper or deprecated fallback usage is not required for this component.

Start with the supplied grep command in src/Administration/Resources/app/administration/src to find all 63 sw-label usages across 36 files. Replace the component tags while preserving props, emitted events, and slot content, then update unit or E2E tests only where selectors or DOM structure changed. Done means the grep finds no in-scope sw-label tags and validation checks component tags rather than internal Meteor DOM classes.

Written by the indexing model from the issue text.