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/person/get.rs

@@ -7,3 +7,7 @@ use domain::{
 pub async fn execute(ctx: &AppContext, id: PersonId) -> Result<Option<Person>, DomainError> {
     ctx.repos.person_query.get_by_id(&id).await
 }
+
+#[cfg(test)]
+#[path = "tests/get.rs"]
+mod tests;

crates/application/src/person/get_credits.rs

@@ -7,3 +7,7 @@ use domain::{
 pub async fn execute(ctx: &AppContext, id: PersonId) -> Result<PersonCredits, DomainError> {
     ctx.repos.person_query.get_credits(&id).await
 }
+
+#[cfg(test)]
+#[path = "tests/get_credits.rs"]
+mod tests;

crates/application/src/person/tests/get.rs

@@ -0,0 +1,16 @@
+use domain::models::PersonId;
+use uuid::Uuid;
+
+use crate::person::get;
+use crate::test_helpers::TestContextBuilder;
+
+#[tokio::test]
+async fn returns_none_for_unknown_person() {
+    let ctx = TestContextBuilder::new().build();
+
+    let result = get::execute(&ctx, PersonId::from_uuid(Uuid::new_v4()))
+        .await
+        .unwrap();
+
+    assert!(result.is_none());
+}

crates/application/src/person/tests/get_credits.rs

@@ -0,0 +1,17 @@
+use domain::models::PersonId;
+use uuid::Uuid;
+
+use crate::person::get_credits;
+use crate::test_helpers::TestContextBuilder;
+
+#[tokio::test]
+async fn returns_empty_credits() {
+    let ctx = TestContextBuilder::new().build();
+
+    let result = get_credits::execute(&ctx, PersonId::from_uuid(Uuid::new_v4()))
+        .await
+        .unwrap();
+
+    assert!(result.cast.is_empty());
+    assert!(result.crew.is_empty());
+}