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/save_profile.rs

@@ -0,0 +1,62 @@
+use std::sync::Arc;
+
+use chrono::Utc;
+use domain::models::ImportSession;
+use domain::ports::ImportSessionRepository;
+use domain::testing::InMemoryImportSessionRepository;
+use domain::value_objects::{ImportSessionId, UserId};
+use uuid::Uuid;
+
+use crate::import::{commands::SaveImportProfileCommand, save_profile};
+use crate::test_helpers::TestContextBuilder;
+
+#[tokio::test]
+async fn fails_when_session_not_found() {
+    let sessions = InMemoryImportSessionRepository::new();
+    let ctx = TestContextBuilder::new()
+        .with_import_sessions(Arc::clone(&sessions) as _)
+        .build();
+
+    let result = save_profile::execute(
+        &ctx,
+        SaveImportProfileCommand {
+            user_id: Uuid::new_v4(),
+            session_id: Uuid::new_v4(),
+            name: "my profile".into(),
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn saves_profile_from_session() {
+    let sessions = InMemoryImportSessionRepository::new();
+    let user_id = Uuid::new_v4();
+    let sid = ImportSessionId::generate();
+
+    let mut session = ImportSession::new(
+        sid.clone(),
+        UserId::from_uuid(user_id),
+        Utc::now().naive_utc(),
+    );
+    session.field_mappings = Some(vec![]);
+    sessions.create(&session).await.unwrap();
+
+    let ctx = TestContextBuilder::new()
+        .with_import_sessions(Arc::clone(&sessions) as _)
+        .build();
+
+    let result = save_profile::execute(
+        &ctx,
+        SaveImportProfileCommand {
+            user_id,
+            session_id: sid.value(),
+            name: "my profile".into(),
+        },
+    )
+    .await;
+
+    assert!(result.is_ok());
+}