fix(calendar): address PR feedback from maintainer

- Remove CHANGELOG.md changes (auto-generated from commits)
- Move all parameter descriptions into function docstrings for LLM context
- Remove unused caldav dependency (using httpx for CalDAV implementation)
- Move datetime imports to top of modules
- Remove load_dotenv from tests/conftest.py
- Clarify Event vs Meeting distinction in docstrings
- Handle 401 auth errors gracefully in calendar tests

Addresses all feedback from PR #95 review

nextcloud_mcp_server/client/calendar.py

@@ -5,7 +5,7 @@ from datetime import datetime, date
 from typing import Dict, Any, List, Optional, Tuple
 import logging
 from httpx import HTTPStatusError
-from icalendar import Calendar, Event as ICalEvent, vRecur
+from icalendar import Calendar, Event as ICalEvent, vRecur, Alarm
 from datetime import timedelta
 import uuid
 
@@ -124,6 +124,12 @@ class CalendarClient(BaseNextcloudClient):
             return calendars
 
         except HTTPStatusError as e:
+            if e.response.status_code == 401:
+                logger.warning("Authentication failed for CalDAV - Calendar app may not be enabled for this user")
+                return []
+            elif e.response.status_code == 404:
+                logger.warning("CalDAV endpoint not found - Calendar app may not be installed")
+                return []
             logger.error(f"HTTP error listing calendars: {e}")
             raise e
         except Exception as e:
@@ -429,7 +435,6 @@ class CalendarClient(BaseNextcloudClient):
         # Add alarms/reminders
         reminder_minutes = event_data.get("reminder_minutes", 0)
         if reminder_minutes > 0:
-            from icalendar import Alarm
 
             alarm = Alarm()
             alarm.add("action", "DISPLAY")