Attempt to fix broken blocks layout when activated with other plugins

fix: improve rewrite rule handling for success page URLs

- Add automatic detection and flushing of missing rewrite rules
- Add admin notice when rewrite rules need updating
- Add debug endpoint for troubleshooting rewrite rule issues
- Add proper deactivation hook to clean up rewrite rules
- Add manual AJAX endpoint for admin-initiated rule flushing

This fixes 404 errors on /paytaca/success/ URLs that occur when
WordPress rewrite rules aren't properly flushed after plugin installation.

Improved composer.json, bumped up plugin version to v0.1.1

Added README file