feat: Implement cron job queue system based on database

- Added PHP support to project configuration.
- Updated FTP configuration to exclude additional directories.
- Changed remote database host in config.php and enabled debug mode.
- Removed outdated TODO from documentation and created a new CRON_QUEUE_PLAN.md.
- Introduced a new cron job queue system using database tables pp_cron_jobs and pp_cron_schedules.
- Refactored cron job orchestration to improve management and reliability.
- Updated OrderAdminService to use the new queue system and removed old file-based logic.
- Added migration scripts for new database structure.

.serena/project.yml

@@ -27,6 +27,7 @@ project_name: "shopPRO"
 # Note that when using the JetBrains backend, language servers are not used and this list is correspondingly ignored.
 languages:
 - typescript
+- php
 
 # the encoding used by text files in the project
 # For a list of possible encodings, see https://docs.python.org/3.11/library/codecs.html#standard-encodings