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

CHANGELOG.md

@@ -1,32 +1,3 @@
-## [Unreleased]
-
-### Feat
-
-- **calendar**: Add comprehensive Calendar app support via CalDAV protocol (Issue #74)
-- **calendar**: Add `nc_calendar_list_calendars` tool for listing available calendars
-- **calendar**: Add `nc_calendar_create_event` tool with full feature support (recurrence, reminders, attendees, categories)
-- **calendar**: Add `nc_calendar_list_events` tool with advanced filtering (date range, attendees, categories, status)
-- **calendar**: Add `nc_calendar_get_event` tool for retrieving detailed event information
-- **calendar**: Add `nc_calendar_update_event` tool for modifying existing events
-- **calendar**: Add `nc_calendar_delete_event` tool for removing events
-- **calendar**: Add `nc_calendar_create_meeting` tool for quick meeting creation with smart defaults
-- **calendar**: Add `nc_calendar_get_upcoming_events` tool for viewing upcoming events
-- **calendar**: Add `nc_calendar_find_availability` tool for intelligent scheduling assistance
-- **calendar**: Add `nc_calendar_bulk_operations` tool for efficient batch event management
-- **calendar**: Add `nc_calendar_manage_calendar` tool for calendar creation and management
-
-### Fix
-
-- **calendar**: Fix type annotations in calendar client for better Pylance compatibility
-- **calendar**: Fix alarm trigger formatting using proper timedelta objects
-- **calendar**: Fix event update handling to merge existing data with new changes
-- **calendar**: Fix categories extraction from icalendar objects
-
-### Refactor
-
-- **calendar**: Implement CalDAV client following existing NextCloud client patterns
-- **calendar**: Add comprehensive calendar integration tests covering all scenarios
-
 ## v0.5.0 (2025-07-26)
 
 ### Feat