Deleted unused e2e tests, mocks (`cuid2`, `jose`, `ml-kem`, `sha3`), and their associated jest configurations. Simplified services by ensuring proper dependency imports, resolving circular references, and improving TypeScript type usage for enhanced maintainability and testability. Upgraded Dockerfile base image to match new development standards.
Introduce foundational database schema with tables for `users`, `categories`, `contents`, `tags`, and `favorites`. Add foreign key relationships, constraints, and indexes for efficient querying.
