add 400+ unit tests for domain and application layers

Extract ReviewLogger trait to decouple import/integrations
from diary::log_review (cross-module coupling smell).

Add in-memory fakes for all repository ports, enabling
isolated testing of every use case module without a database.

Coverage: domain+application 22% → 80%, 427 tests.

crates/application/src/diary/mod.rs

@@ -8,3 +8,4 @@ pub mod get_review_history;
 pub mod log_review;
 pub mod movie_resolver;
 pub mod queries;
+pub mod review_logger;