feat(domain): add find_by_id to UserRepository + SQLite impl

crates/adapters/sqlite/src/users.rs

@@ -73,4 +73,79 @@ impl UserRepository for SqliteUserRepository {
 
         Ok(())
     }
+
+    async fn find_by_id(&self, id: &UserId) -> Result<Option<User>, DomainError> {
+        let id_str = id.value().to_string();
+        let row = sqlx::query!(
+            "SELECT id, email, password_hash FROM users WHERE id = ?",
+            id_str
+        )
+        .fetch_optional(&self.pool)
+        .await
+        .map_err(Self::map_err)?;
+
+        match row {
+            None => Ok(None),
+            Some(r) => {
+                let uuid = uuid::Uuid::parse_str(&r.id)
+                    .map_err(|e| DomainError::InfrastructureError(e.to_string()))?;
+                let email = Email::new(r.email)
+                    .map_err(|e| DomainError::InfrastructureError(e.to_string()))?;
+                let hash = PasswordHash::new(r.password_hash)
+                    .map_err(|e| DomainError::InfrastructureError(e.to_string()))?;
+                Ok(Some(User::from_persistence(UserId::from_uuid(uuid), email, hash)))
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use sqlx::SqlitePool;
+
+    async fn setup() -> (SqlitePool, SqliteUserRepository) {
+        let pool = SqlitePool::connect(":memory:").await.unwrap();
+        sqlx::query(
+            "CREATE TABLE users (id TEXT PRIMARY KEY, email TEXT NOT NULL UNIQUE, password_hash TEXT NOT NULL, created_at TEXT NOT NULL)"
+        )
+        .execute(&pool)
+        .await
+        .unwrap();
+        let repo = SqliteUserRepository::new(pool.clone());
+        (pool, repo)
+    }
+
+    #[tokio::test]
+    async fn find_by_id_returns_none_when_not_found() {
+        let (_, repo) = setup().await;
+        let result = repo
+            .find_by_id(&UserId::from_uuid(uuid::Uuid::new_v4()))
+            .await
+            .unwrap();
+        assert!(result.is_none());
+    }
+
+    #[tokio::test]
+    async fn find_by_id_returns_user_when_found() {
+        let (pool, repo) = setup().await;
+        let id = uuid::Uuid::new_v4();
+        sqlx::query(
+            "INSERT INTO users (id, email, password_hash, created_at) VALUES (?, ?, ?, ?)"
+        )
+        .bind(id.to_string())
+        .bind("test@example.com")
+        .bind("$argon2id$v=19$m=65536,t=2,p=1$fakesalt$fakehash")
+        .bind("2026-01-01T00:00:00Z")
+        .execute(&pool)
+        .await
+        .unwrap();
+
+        let result = repo
+            .find_by_id(&UserId::from_uuid(id))
+            .await
+            .unwrap();
+        assert!(result.is_some());
+        assert_eq!(result.unwrap().email().value(), "test@example.com");
+    }
 }