fix: warn on silent data loss in report

Issues not returned by issue.filter (no access / deleted) and failures
of the time entry activities lookup were silently swallowed: the report
was built from partial data without telling the user.

Now both cases emit a warning to stderr (project ⚠️ style, #28):
- skipped issue IDs and total lost hours after issue matching;
- activities lookup failure (still returns {} and falls back to
  activity names from time entries).

These are warnings, not errors: the report is still built from
available data and the exit code is unchanged.

Closes #61

tests/test_client.py

@@ -969,3 +969,111 @@ def test_dedup_accepts_naive_cutoff(mock_redmine_class):
 
     assert result is not None
     assert [r[0].id for r in result] == [2]
+
+
+# -- #61: предупреждения о молчаливой потере данных --
+
+
+@mock.patch.dict(os.environ, PASSWORD_ENV, clear=True)
+@mock.patch("redmine_reporter.client.Redmine")
+def test_fetch_warns_about_missing_issues(mock_redmine_class, capsys):
+    """Задачи, не вернувшиеся из issue.filter, попадают в warning в stderr (#61).
+
+    Отчёт при этом строится по доступным данным — это предупреждение, не ошибка.
+    """
+    mock_redmine = mock_redmine_class.return_value
+    _configure_current_user(mock_redmine, user_id=123)
+
+    def make_entry(issue_id, hours):
+        e = mock.MagicMock()
+        e.issue.id = issue_id
+        e.hours = hours
+        return e
+
+    mock_redmine.time_entry.filter.return_value = [
+        make_entry(1, 1.0),
+        make_entry(2, 2.5),
+        make_entry(3, 0.75),
+    ]
+
+    mock_issue1 = mock.MagicMock()
+    mock_issue1.id = 1
+    mock_issue1.project = "P"
+    mock_issue1.subject = "T"
+    mock_issue1.status = "New"
+    # Задачи 2 и 3 не вернулись (нет прав / удалены)
+    mock_redmine.issue.filter.return_value = [mock_issue1]
+
+    result = fetch_issues_with_spent_time("2026-01-01", "2026-01-31")
+
+    assert result is not None
+    assert [r[0].id for r in result] == [1]
+
+    captured = capsys.readouterr()
+    assert "2" in captured.err
+    assert "3" in captured.err
+    assert "3.25" in captured.err  # сумма потерянных часов 2.5 + 0.75
+
+
+@mock.patch.dict(os.environ, PASSWORD_ENV, clear=True)
+@mock.patch("redmine_reporter.client.Redmine")
+def test_fetch_no_warning_when_all_issues_returned(mock_redmine_class, capsys):
+    """Если все задачи вернулись, stderr остаётся чистым (#61)."""
+    mock_redmine = mock_redmine_class.return_value
+    _configure_current_user(mock_redmine, user_id=123)
+
+    e = mock.MagicMock()
+    e.issue.id = 1
+    e.hours = 1.0
+    mock_redmine.time_entry.filter.return_value = [e]
+
+    mock_issue1 = mock.MagicMock()
+    mock_issue1.id = 1
+    mock_redmine.issue.filter.return_value = [mock_issue1]
+
+    result = fetch_issues_with_spent_time("2026-01-01", "2026-01-31")
+
+    assert result is not None
+    captured = capsys.readouterr()
+    assert captured.err == ""
+
+
+@mock.patch.dict(os.environ, PASSWORD_ENV, clear=True)
+@mock.patch("redmine_reporter.client.Redmine")
+def test_fetch_warns_when_activities_lookup_fails(mock_redmine_class, capsys):
+    """Сбой справочника активностей — warning в stderr, отчёт строится (#61)."""
+    mock_redmine = mock_redmine_class.return_value
+    _configure_current_user(mock_redmine, user_id=123)
+    mock_redmine.enumeration.filter.side_effect = Exception("enumeration boom")
+
+    e = mock.MagicMock()
+    e.issue.id = 1
+    e.hours = 1.0
+    e.activity.id = 9
+    e.activity.name = "Dev"
+    mock_redmine.time_entry.filter.return_value = [e]
+
+    mock_issue1 = mock.MagicMock()
+    mock_issue1.id = 1
+    mock_redmine.issue.filter.return_value = [mock_issue1]
+
+    result = fetch_issues_with_spent_time("2026-01-01", "2026-01-31", by_activity=True)
+
+    assert result is not None
+    assert result[0][2] == {"Dev": 1.0}  # fallback на имя из самого entry
+
+    captured = capsys.readouterr()
+    assert "activit" in captured.err.lower()
+
+
+def test_load_time_entry_activities_returns_empty_on_failure(capsys):
+    """_load_time_entry_activities возвращает {} и пишет warning при сбое (#61)."""
+    from redmine_reporter.client import _load_time_entry_activities
+
+    redmine = mock.MagicMock()
+    redmine.enumeration.filter.side_effect = Exception("enumeration boom")
+
+    assert _load_time_entry_activities(redmine) == {}
+
+    captured = capsys.readouterr()
+    assert "activit" in captured.err.lower()