Mem-Client: No Emotion Object Style Syntax

MDS style files must use Emotion tagged-template syntax.

Rationale:
- Tagged templates match team style conventions and keep style declarations consistent.

Scope:
- PR review policy for `domains/frontend/mem-client/src/mds/components/**/*.style.tsx`.

Trigger:
- A PR adds or changes styled component definitions in scope.

Approval checks:
1) Styled definitions use tagged-template syntax.
2) Object-style Emotion syntax (for example `styled(Component)({ ... })`) is not introduced.

Evidence:
- Diff of style files shows tagged-template usage only.

Decision:
- Return NOT APPROVED when trigger is met and object-style syntax is introduced.