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

tests/conftest.py

@@ -5,10 +5,6 @@ import uuid
 from nextcloud_mcp_server.client import NextcloudClient
 from httpx import HTTPStatusError
 import asyncio
-from dotenv import load_dotenv
-
-# Load environment variables from .env file
-load_dotenv()
 
 logger = logging.getLogger(__name__)