test(kyc): nationality + 2FA request + 2FA verify cubits (+9 tests)

[TaprootFreak]

Summary

Stage 47 of the coverage push. Cubit-level coverage of three related KYC step cubits.

Cases

Target	Cases
`KycNationalityCubit`	3 — initial state; `setData` fires with `{nationality: {id: }}` + Loading → Success; failure path
`Kyc2FaCubit` (request)	3 — initial state; Loading → Success on `request2FaCode`; Loading → Failure on throw
`Kyc2FaVerifyCubit` (verify)	3 — initial state; Loading → Success on `verify2FaCode`; Loading → Failure on throw

What's pinned

• The nationality body shape is `{nationality: {id: }}` — pinned verbatim so a refactor doesn't quietly invert it (e.g. `{nationalityId: }`).
• Both 2FA cubits carry the raw `e.toString()` into the failure state's `errorMessage` — the UI uses that as fallback copy, so the contract is pinned.

Test plan

• `flutter test test/screens/kyc/steps/kyc_nationality_2fa_cubits_test.dart` — 9 pass
• `flutter analyze` clean on the new file
• CI green