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/domain/src/models/goal.rs

@@ -109,3 +109,98 @@ impl GoalWithProgress {
         self.current_count >= self.goal.target_count
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::value_objects::UserId;
+
+    fn make_goal(year: u16, target: u32) -> Result<Goal, DomainError> {
+        Goal::new(UserId::generate(), year, target, GoalType::Movies)
+    }
+
+    #[test]
+    fn new_goal_valid() {
+        let g = make_goal(2024, 52);
+        assert!(g.is_ok());
+        let g = g.unwrap();
+        assert_eq!(g.year(), 2024);
+        assert_eq!(g.target_count(), 52);
+    }
+
+    #[test]
+    fn new_goal_rejects_year_before_2020() {
+        assert!(make_goal(2019, 10).is_err());
+    }
+
+    #[test]
+    fn new_goal_rejects_zero_target() {
+        assert!(make_goal(2024, 0).is_err());
+    }
+
+    #[test]
+    fn update_target_valid() {
+        let mut g = make_goal(2024, 10).unwrap();
+        assert!(g.update_target(50).is_ok());
+        assert_eq!(g.target_count(), 50);
+    }
+
+    #[test]
+    fn update_target_rejects_zero() {
+        let mut g = make_goal(2024, 10).unwrap();
+        assert!(g.update_target(0).is_err());
+    }
+
+    #[test]
+    fn from_persistence_preserves_fields() {
+        let id = GoalId::generate();
+        let uid = UserId::generate();
+        let ts = chrono::Utc::now().naive_utc();
+        let g = Goal::from_persistence(id.clone(), uid.clone(), 2025, 42, GoalType::Movies, ts);
+        assert_eq!(*g.id(), id);
+        assert_eq!(*g.user_id(), uid);
+        assert_eq!(g.year(), 2025);
+        assert_eq!(g.target_count(), 42);
+        assert_eq!(g.created_at(), &ts);
+    }
+
+    #[test]
+    fn percentage_calculation() {
+        let g = make_goal(2024, 100).unwrap();
+        let wp = GoalWithProgress {
+            goal: g,
+            current_count: 50,
+        };
+        assert!((wp.percentage() - 50.0).abs() < f64::EPSILON);
+    }
+
+    #[test]
+    fn percentage_caps_at_100() {
+        let g = make_goal(2024, 10).unwrap();
+        let wp = GoalWithProgress {
+            goal: g,
+            current_count: 20,
+        };
+        assert!((wp.percentage() - 100.0).abs() < f64::EPSILON);
+    }
+
+    #[test]
+    fn is_complete() {
+        let g = make_goal(2024, 10).unwrap();
+        let wp = GoalWithProgress {
+            goal: g,
+            current_count: 10,
+        };
+        assert!(wp.is_complete());
+    }
+
+    #[test]
+    fn is_not_complete() {
+        let g = make_goal(2024, 10).unwrap();
+        let wp = GoalWithProgress {
+            goal: g,
+            current_count: 9,
+        };
+        assert!(!wp.is_complete());
+    }
+}