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/import/tests/apply_profile.rs

@@ -0,0 +1,115 @@
+use std::sync::Arc;
+
+use chrono::Utc;
+use domain::models::ImportProfile;
+use domain::ports::{ImportProfileRepository, ImportSessionRepository};
+use domain::testing::InMemoryImportProfileRepository;
+use domain::value_objects::{ImportProfileId, UserId};
+use uuid::Uuid;
+
+use crate::import::{apply_profile, commands::ApplyImportProfileCommand};
+use crate::test_helpers::TestContextBuilder;
+
+#[tokio::test]
+async fn fails_when_profile_not_found() {
+    let ctx = TestContextBuilder::new().build();
+
+    let result = apply_profile::execute(
+        &ctx,
+        ApplyImportProfileCommand {
+            user_id: Uuid::new_v4(),
+            session_id: Uuid::new_v4(),
+            profile_id: Uuid::new_v4(),
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn fails_when_session_not_found() {
+    let profiles = InMemoryImportProfileRepository::new();
+    let user_id = Uuid::new_v4();
+
+    let profile = ImportProfile::new(
+        ImportProfileId::generate(),
+        UserId::from_uuid(user_id),
+        "test".into(),
+        vec![],
+        Utc::now().naive_utc(),
+    );
+    let profile_id = profile.id.clone();
+    profiles.save(&profile).await.unwrap();
+
+    let ctx = TestContextBuilder::new()
+        .with_import_profiles(Arc::clone(&profiles) as _)
+        .build();
+
+    let result = apply_profile::execute(
+        &ctx,
+        ApplyImportProfileCommand {
+            user_id,
+            session_id: Uuid::new_v4(),
+            profile_id: profile_id.value(),
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn applies_profile_mappings_to_session() {
+    let profiles = InMemoryImportProfileRepository::new();
+    let sessions = domain::testing::InMemoryImportSessionRepository::new();
+    let user_id = Uuid::new_v4();
+
+    let profile = ImportProfile::new(
+        ImportProfileId::generate(),
+        UserId::from_uuid(user_id),
+        "letterboxd".into(),
+        vec![domain::models::FieldMapping {
+            source_column: "Name".into(),
+            domain_field: domain::models::import::DomainField::Title,
+            transform: domain::models::import::Transform::Identity,
+        }],
+        Utc::now().naive_utc(),
+    );
+    let profile_id = profile.id.clone();
+    profiles.save(&profile).await.unwrap();
+
+    let session = domain::models::ImportSession::new(
+        domain::value_objects::ImportSessionId::generate(),
+        UserId::from_uuid(user_id),
+        Utc::now().naive_utc(),
+    );
+    let session_id = session.id.clone();
+    sessions.create(&session).await.unwrap();
+
+    let ctx = TestContextBuilder::new()
+        .with_import_profiles(Arc::clone(&profiles) as _)
+        .with_import_sessions(Arc::clone(&sessions) as _)
+        .build();
+
+    apply_profile::execute(
+        &ctx,
+        ApplyImportProfileCommand {
+            user_id,
+            session_id: session_id.value(),
+            profile_id: profile_id.value(),
+        },
+    )
+    .await
+    .unwrap();
+
+    // Verify the session got updated with field_mappings and row_results cleared
+    let updated = sessions
+        .get(&session_id, &UserId::from_uuid(user_id))
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(updated.field_mappings.is_some());
+    assert_eq!(updated.field_mappings.unwrap().len(), 1);
+    assert!(updated.row_results.is_none());
+}