Fix Routing Urls

[Z3d0X]

• Fix route prefixing
• Fix inconsistent routing
• Restrict slugs starting/ending with slashes(/) (except homepage)

[what-the-diff[bot]]

• Added a new validation rule to the slug field.
• Fixed some issues with routing prefixes and page URLs in various places of the package codebase, including:
  • The FilamentFabricator::getRoutingPrefix() method now returns an empty string instead of null if no custom routing prefix is set (this fixes an issue where pages would not be accessible when using Laravel's default route model binding).
  • Page URL values are always prefixed with a slash character ('/') for consistency reasons. This also makes it possible to use relative paths as slugs without having them being treated as absolute ones by Filament Fabricator itself or other parts of your application that might rely on this behavior (e.g., Nova's resource actions).