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/goals/tests/create.rs

@@ -0,0 +1,117 @@
+use std::sync::Arc;
+
+use domain::events::DomainEvent;
+use domain::testing::{InMemoryGoalRepository, NoopEventPublisher};
+use uuid::Uuid;
+
+use crate::goals::{commands::CreateGoalCommand, create};
+use crate::test_helpers::TestContextBuilder;
+
+#[tokio::test]
+async fn creates_goal_and_returns_progress() {
+    let goals = InMemoryGoalRepository::new();
+    goals.set_review_count(Uuid::nil(), 2025, 5);
+    let events = NoopEventPublisher::new();
+    let ctx = TestContextBuilder::new()
+        .with_goal(Arc::clone(&goals) as _)
+        .with_event_publisher(Arc::clone(&events) as _)
+        .build();
+
+    let result = create::execute(
+        &ctx,
+        CreateGoalCommand {
+            user_id: Uuid::nil(),
+            year: 2025,
+            target_count: 50,
+        },
+    )
+    .await
+    .unwrap();
+
+    assert_eq!(result.goal.year(), 2025);
+    assert_eq!(result.goal.target_count(), 50);
+    assert_eq!(result.current_count, 5);
+    assert_eq!(goals.count(), 1);
+}
+
+#[tokio::test]
+async fn emits_goal_created_event() {
+    let events = NoopEventPublisher::new();
+    let ctx = TestContextBuilder::new()
+        .with_event_publisher(Arc::clone(&events) as _)
+        .build();
+
+    create::execute(
+        &ctx,
+        CreateGoalCommand {
+            user_id: Uuid::nil(),
+            year: 2025,
+            target_count: 10,
+        },
+    )
+    .await
+    .unwrap();
+
+    let published = events.published();
+    assert!(
+        published
+            .iter()
+            .any(|e| matches!(e, DomainEvent::GoalCreated { year: 2025, .. }))
+    );
+}
+
+#[tokio::test]
+async fn rejects_duplicate_year() {
+    let ctx = TestContextBuilder::new().build();
+    let cmd = CreateGoalCommand {
+        user_id: Uuid::nil(),
+        year: 2025,
+        target_count: 10,
+    };
+
+    create::execute(&ctx, cmd).await.unwrap();
+
+    let result = create::execute(
+        &ctx,
+        CreateGoalCommand {
+            user_id: Uuid::nil(),
+            year: 2025,
+            target_count: 20,
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn rejects_year_before_2020() {
+    let ctx = TestContextBuilder::new().build();
+    let result = create::execute(
+        &ctx,
+        CreateGoalCommand {
+            user_id: Uuid::nil(),
+            year: 2019,
+            target_count: 10,
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn rejects_zero_target() {
+    let ctx = TestContextBuilder::new().build();
+    let result = create::execute(
+        &ctx,
+        CreateGoalCommand {
+            user_id: Uuid::nil(),
+            year: 2025,
+            target_count: 0,
+        },
+    )
+    .await;
+
+    assert!(result.is_err());
+}