Extract Admin Tools UI from CampTix_Plugin into CampTix_Admin_Tools

Move the Tickets > Tools page UI methods (Summarize, Revenue, Export,
Notify, Refund tabs) into a dedicated inc/class-camptix-admin-tools.php
file. Data/utility methods (get_summary, generate_revenue_report_data,
get_segment, etc.) remain in CampTix_Plugin.

camptix.php: 8,445 -> 7,587 lines (-858)

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

Author: dd32