test(astrolabe): add comprehensive unit tests for token refresh and storage
Add unit tests addressing reviewer feedback on test coverage gaps:
IdpTokenRefresher::refreshAccessToken() tests:
- Token refresh with internal Nextcloud OIDC
- Token refresh with external IdP (Keycloak)
- Error handling: missing client_secret, missing MCP URL
- Error handling: invalid responses, HTTP exceptions
- Token rotation validation (missing refresh_token in response)
McpTokenStorage tests (multi-user basic auth):
- OAuth token storage, retrieval, deletion
- Token expiration checks with 60-second buffer
- getAccessToken with automatic refresh callback
- App password storage for background sync
- hasBackgroundSyncAccess() for both OAuth and app passwords
- Background sync type detection and timestamp tracking
Test coverage: 41 tests, 76 assertions (up from 5 tests)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
