Major refactoring to reduce code duplication and address security concerns:

* feat(__api_request): consolidate retry logic into _request_with_retry
  - Extract HTTP operations into inner functions (_do_get, _do_post, etc.)
  - Centralize error handling for all HTTP methods
  - Reduces code duplication by ~55 lines

* security(__api_session): remove SSL verification bypass in Vault client
  - Remove verify=False from hvac.Client initialization
  - Make vault attributes private (_vault_url, _vault_path, etc.)
  - Improve vault credentials cleanup in finally block

* feat(__api_session): improve session management
  - Add _new_session() helper for consistent session initialization
  - Add validate parameter to set_api_token() for optional token validation
  - Fix delete_api_token() to return APIResponse instead of Response
  - Use mist_delete() method instead of raw session.delete()

* perf(__init__): implement lazy loading for heavy subpackages
  - Defer api and cli imports until accessed
  - Improves initial import performance

* fix(__logger): correct logging sanitization
  - Use getMessage() instead of direct msg access
  - Clear record.args after sanitization to prevent re-formatting

This refactoring improves maintainability, security, and performance without
changing the public API surface.

  refactor: rename utils to device_utils and adopt camelCase public API

  Reorganize device utility modules from `mistapi.utils` to
  `mistapi.device_utils` with a clean separation between internal
  implementations (`__tools/`) and public-facing device modules
  (ap, ex, srx, ssr). Public function names now use camelCase
  (e.g. retrieveArpTable, monitorTraffic) for consistency with the
  auto-generated REST API.

  Also adds comprehensive unit tests for api_request, api_response,
  api_session, models, pagination, logger, init, and websocket_client.

- Updated `searchOrgNacClients` and `searchSiteNacClients` to correct status options from 'session_ended' to 'session_stopped'.
- Rearranged parameters in `searchOrgWanClients`, `searchSiteWanClients`, and `searchSiteWirelessClients` for consistency and clarity.
- Added new parameters `cert_expiry_duration` and `psk_name` to `searchSiteNacClients` and `searchSiteWirelessClients` respectively.
- Removed unused parameters and cleaned up query parameter handling in various search functions.
- Enhanced logging and sanitization in `test_logger.py` to ensure sensitive data is properly redacted.
- Deleted obsolete test file `test.py` to streamline the test suite.
- Improved test readability and structure across multiple test files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>