feat: explain activity data quality

apps/api/tests/test_activity.py

@@ -86,7 +86,17 @@ def test_repeated_reports_from_one_player_do_not_add_unique_player_weight(db: Se
 
     assert row.catches == 3
     assert row.unique_players == 1
-    assert "3 свежих уловов от 1 игроков" in row.explanation
+    assert "3 свежих улова от 1 игрока" in row.explanation
+
+
+def test_explanation_describes_low_data_and_confidence(db: Session) -> None:
+    add_report(db, age_hours=2, player="Player", confidence=50)
+
+    row = activity_rows(db, hours=6, now=NOW)[0]
+
+    assert row.explanation.startswith("Низкая активность: 1 свежий улов от 1 игрока.")
+    assert "Уверенность низкая." in row.explanation
+    assert "Данных мало: нужно хотя бы 3 наблюдения." in row.explanation
 
 
 def test_pending_rejected_and_deleted_reports_are_excluded(db: Session) -> None:

apps/api/tests/test_api.py

@@ -46,11 +46,12 @@ def test_activity_filters_and_explains_score() -> None:
     assert len(payload) == 1
     assert payload[0]["catches"] == 3
     assert payload[0]["unique_players"] == 3
-    assert "3 свежих уловов" in payload[0]["explanation"]
+    assert "3 свежих улова" in payload[0]["explanation"]
 
 
 def test_invalid_period_is_rejected() -> None:
     assert client.get("/api/v1/activity?hours=13").status_code == 422
+    assert client.get("/api/v1/activity?sort=unknown").status_code == 422
 
 
 def test_spot_detail_and_catches() -> None: