Mem-Client: Exported Literal Collections Use as const

Exported literal collections in constants files must use `as const`.

Rationale:
- `as const` preserves immutable literal types and prevents widening.

Scope:
- PR review policy for `domains/frontend/mem-client/src/**/constants.ts`.

Trigger:
- A PR adds or changes exported array/object literal constants (named export or default export literal initializer).

Approval checks:
1) Each exported literal array/object initializer uses `as const` on the declaration.

Evidence:
- Diff shows `as const` on each new/changed exported literal collection.

Decision:
- Return NOT APPROVED when trigger is met and `as const` is missing.