Unit tests: data models and role guard

Generate mockito mocks with build_runner (@GenerateMocks annotation) placed in a test/helpers/mocks.dart file shared across test files. Use fixtures (static factory methods or JSON files in test/fixtures/) to reduce boilerplate. For copyWith edge cases, test: updating every field individually, updating no fields (returns equal object), and chaining copyWith twice. For enum boundary tests, iterate over MyEnum.values in a for-loop test rather than writing one test per value — this ensures new enum values automatically get tested.

For CoordinatorRoleGuard, create a thin FakeAuthStateNotifier that extends StateNotifier and exposes a setRole(UserRole?) method to drive guard state without async complexity.

Pure unit tests using flutter_test. No widget tests or integration tests in this task. Use ProviderContainer (not ProviderScope) for Riverpod-dependent guard tests to keep them lightweight. Use mockito-generated mocks for any auth state dependency injected into CoordinatorRoleGuard.

Organise tests in describe-style group() blocks: one group per class, nested groups per method/scenario. Each test must have a descriptive name following the pattern 'given [state] when [action] then [expectation]'. Verify that fromJson raises a meaningful FormatException (not a null crash) when required fields are missing.