WebCalendar v1.9.17

Maintenance release focused on the install/upgrade wizard's PHP 8.1+ compatibility, plus a TinyMCE security update and several smaller fixes.

Security

Prevent "Unexpected end of JSON input" during install/upgrade on PHP 8.1+; the wizard now returns proper JSON instead of an empty body on database errors (#642)
Restore missing wizard methods so the admin-user and upgrade-SQL steps work again (createAdminUser, getUpgradeSqlCommands) (#642)
Ship the TinyMCE table plugin referenced by the editor configuration
Guard count() against null in RSS feed generation on PHP 8
Return MCP event times in the user's local timezone
Repair MCP add_event and rate limiting, and isolate the MCP test suite
Handle mixed latin1/UTF-8 data in the charset conversion tool

WebCalendar releases ship a signed manifest. See docs/release-signing.md for verification instructions.