Introduce `getPublicUrl` in `S3Service` for generating public URLs. Replace custom file URL generation logic across services with the new method. Add media controller for file streaming and update related tests. Adjust frontend to display user roles instead of email in the sidebar. Update environment schema to include optional `API_URL`. Fix help page contact email.
Optimized import order, applied consistent formatting, and improved readability in various modules, including `contents`, `media`, and `auth` services.
Introduced `env.schema.ts` for structured validation of environment variables using Zod. Includes defaults and validations for database, S3, security, mail, Redis, and session configurations.
