Add SEO-friendly routes and implement slug migrations for users and samples

Commit notes

- Introduced new routes for creators and their packs/samples, enhancing the URL structure for better SEO: `/creator/:creatorSlug`, `/creator/:creatorSlug/pack/:packSlug`, and `/creator/:creatorSlug/pack/:packSlug/sample/:sampleSlug`. - Implemented migrations to add unique slugs for existing users and samples, ensuring proper indexing and validation. - Updated relevant handlers to utilize slugs in responses, improving data retrieval and user experience. - Enhanced frontend routing to reflect the new structure, ensuring seamless navigation across creator and sample pages.