feat: gold standards tests (15 days + STT + vision) & botName editable in AI setup

feat(billing): complete billing system, push notifications, and tech debt fixes

feat: backlog P0→P3 — toast system, payments, tenant isolation, feedback handler, i18n parity

chore: stabilization, audit fixes and project synchronization

fix: correct StripeService constructor call in tests

feat: complete final technical debt polishing (structured logs, stripe tests, and automated migrations)

fix: resolve test import errors and export AIService class

chore: optimize Dockerfile and PM2 config for independent scaling and better performance

chore: implement Phase 3 initial setup (TypeScript cleanup and health test)

Chore: Added AI regression test framework and enhanced Mock provider