feat: domain mocks, TestContextBuilder, use case tests, factory pattern

- Add test-helpers feature to domain crate with in-memory mocks and panic stubs for all ports
- Add TestContextBuilder to application crate for zero-database test setup
- Add unit tests for log_review, register, login, add_to_watchlist, delete_review use cases
- Extract DatabaseAdapters factory and build_* helpers into presentation/src/factory.rs
- Refactor wire_dependencies() in main.rs to use factory module

crates/domain/Cargo.toml

@@ -11,3 +11,6 @@ thiserror = { workspace = true }
 futures = { workspace = true }
 
 email_address = "0.2.9"
+
+[features]
+test-helpers = []