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

redmine_reporter/client.py

@@ -1,3 +1,4 @@
+import sys
 from datetime import datetime, timezone
 from typing import Any, Dict, List, Optional, Tuple, Union
 
@@ -121,7 +122,14 @@ def _load_time_entry_activities(redmine: Redmine) -> Dict[int, str]:
     try:
         activities = redmine.enumeration.filter(resource="time_entry_activities")
         return {int(a.id): str(a.name) for a in activities}
-    except Exception:
+    except Exception as exc:
+        # #61: не глотаем сбой молча — предупреждаем, что разбивка по
+        # активностям будет построена по сырым данным из самих entries.
+        print(
+            f"⚠️  Could not load time entry activities: {exc}. "
+            "Activity names will be taken from time entries.",
+            file=sys.stderr,
+        )
         return {}
 
 
@@ -346,6 +354,20 @@ def fetch_issues_with_spent_time(
     except Exception as exc:
         raise RedmineAPIError(_format_redmine_error(exc), original=exc) from exc
 
+    # #61: задачи могли не вернуться из issue.filter (нет прав / удалены) —
+    # предупреждаем о выпавших задачах и потерянных часах, но строим отчёт
+    # по доступным данным.
+    returned_ids = {issue.id for issue in issues}
+    missing_ids = sorted(issue_ids - returned_ids)
+    if missing_ids:
+        lost_hours = sum(spent_time[iid] for iid in missing_ids)
+        print(
+            f"⚠️  {len(missing_ids)} issue(s) unavailable (no access or deleted; "
+            f"IDs: {', '.join(str(i) for i in missing_ids)}): "
+            f"{lost_hours:g}h excluded from the report.",
+            file=sys.stderr,
+        )
+
     # Сопоставляем задачи с суммарным временем.
     # Сортировка выполняется в report_builder.build_grouped_report,
     # здесь оставляем порядок API как есть.