Write integration tests for repository and audit logger layers

Create a test helper class SupabaseTestHelper that wraps client initialization, row seeding, and cleanup to reduce boilerplate across test files. For soft-delete tests, use two queries: one with the default filter (should exclude deleted) and one with includeDeleted: true (should include) to verify both paths. For lifecycle transition tests, seed a declaration in the starting state, call the repository transition method, then re-fetch and assert the new status. For audit log insert-only enforcement, catch the PostgrestException and assert its message or code indicates a policy violation — do not rely on HTTP status codes alone as they can vary.

Document which Supabase project is used for integration tests in a README inside test/integration/.

These ARE the tests. Use flutter_test with a test/integration/ directory. Each repository gets its own test file (declaration_template_repository_test.dart, driver_assignment_repository_test.dart, declaration_repository_test.dart, declaration_audit_logger_test.dart). Use setUp/tearDown to insert and delete test rows using a privileged service-role Supabase client.

For RLS tests, initialize a second SupabaseClient with org_B credentials and assert that queries return empty lists. The test Supabase project URL and anon/service-role keys must be injected via --dart-define or a .env file excluded from version control. Tag integration tests with @Tags(['integration']) so they can be excluded from fast unit test runs.