Refactor insights handling and error encoding in presentation layer

- Updated insights analyzer tests to use Utc for date handling.
- Added timezone support for insights retrieval, allowing insights to be bucketed by the user's local time.
- Introduced `encode_domain_error` for better error handling in API responses.
- Modified various handlers to utilize the new error encoding function.
- Enhanced insights API to reject unknown time zones and return appropriate errors.
- Updated frontend components to handle insights data with timezone awareness.
- Improved localization for insights sample counts.

crates/server/tests/api_test.rs

@@ -744,3 +744,103 @@ async fn get_api_insights_returns_rating_lift_for_own_user() {
     assert_eq!(rhythm["peak_hour_end"], 14);
     assert_eq!(rhythm["top_days"], serde_json::json!([5, 7]));
 }
+
+async fn get_insights_json(
+    app: Router,
+    user_id: Uuid,
+    query: &str,
+) -> (StatusCode, serde_json::Value) {
+    let response = app
+        .oneshot(with_ip(
+            Request::builder()
+                .uri(format!("/api/v1/insights{query}"))
+                .header("authorization", format!("Bearer {user_id}"))
+                .body(Body::empty())
+                .unwrap(),
+        ))
+        .await
+        .unwrap();
+    let status = response.status();
+    let bytes = response.into_body().collect().await.unwrap().to_bytes();
+    let json = serde_json::from_slice(&bytes).unwrap_or(serde_json::Value::Null);
+    (status, json)
+}
+
+#[tokio::test]
+async fn get_api_insights_ignores_remote_reviews() {
+    let (app, pool) = test_app_with(domain::testing::FakeAuthService).await;
+    let user_id = Uuid::new_v4();
+    seed_insights_diary(&pool, user_id).await;
+    // Federated rows stored under the same user_id are someone else's watches.
+    for i in 0..12u32 {
+        let movie_id = uuid::Uuid::new_v4().to_string();
+        sqlx::query("INSERT INTO movies (id, title, release_year) VALUES (?, ?, ?)")
+            .bind(&movie_id)
+            .bind(format!("Horror {i}"))
+            .bind(2019)
+            .execute(&pool)
+            .await
+            .unwrap();
+        sqlx::query("INSERT INTO movie_genres (movie_id, tmdb_id, name) VALUES (?, ?, ?)")
+            .bind(&movie_id)
+            .bind(66600 + i as i64)
+            .bind("Horror")
+            .execute(&pool)
+            .await
+            .unwrap();
+        sqlx::query(
+            "INSERT INTO reviews (id, movie_id, user_id, rating, watched_at, created_at, remote_actor_url) \
+             VALUES (?, ?, ?, ?, ?, ?, ?)",
+        )
+        .bind(uuid::Uuid::new_v4().to_string())
+        .bind(&movie_id)
+        .bind(user_id.to_string())
+        .bind(5)
+        .bind("2024-05-05 09:00:00")
+        .bind("2024-05-05 09:00:00")
+        .bind("https://remote.example/users/someone")
+        .execute(&pool)
+        .await
+        .unwrap();
+    }
+
+    let (status, json) = get_insights_json(app, user_id, "").await;
+    assert_eq!(status, StatusCode::OK);
+    let insights = json["insights"].as_array().unwrap();
+    assert!(
+        !insights.iter().any(|i| i["genre"] == "Horror"),
+        "remote reviews must not feed insights: {json}"
+    );
+    let thriller = insights
+        .iter()
+        .find(|i| i["kind"] == "rating_lift" && i["genre"] == "Thriller")
+        .unwrap();
+    assert_eq!(thriller["delta"], 1.5);
+}
+
+#[tokio::test]
+async fn get_api_insights_buckets_rhythm_in_requested_time_zone() {
+    let (app, pool) = test_app_with(domain::testing::FakeAuthService).await;
+    let user_id = Uuid::new_v4();
+    seed_insights_diary(&pool, user_id).await;
+
+    // January in Warsaw is UTC+1: 22:30 → 23:30 and 13:00 → 14:00, so the
+    // earliest tied window moves from 11–14 to 12–15.
+    let (status, json) = get_insights_json(app, user_id, "?tz=Europe/Warsaw").await;
+    assert_eq!(status, StatusCode::OK);
+    let rhythm = json["insights"]
+        .as_array()
+        .unwrap()
+        .iter()
+        .find(|i| i["kind"] == "rhythm")
+        .expect("rhythm expected");
+    assert_eq!(rhythm["peak_hour_start"], 12);
+    assert_eq!(rhythm["peak_hour_end"], 15);
+}
+
+#[tokio::test]
+async fn get_api_insights_rejects_unknown_time_zone() {
+    let (app, _pool) = test_app_with(domain::testing::FakeAuthService).await;
+    let (status, _) = get_insights_json(app, Uuid::new_v4(), "?tz=Mars/Olympus").await;
+    assert_eq!(status, StatusCode::BAD_REQUEST);
+}