feat: Implement Multiple Categories per Record with Approval System

This pull request introduces a comprehensive overhaul of the category system, enabling records to be associated with multiple categories and implementing a robust approval workflow for new category submissions.

Key Features & Changes:

• Multiple Categories per Record:

  • The data model has been updated to allow a single record to be tagged with multiple categories, providing greater flexibility in content organization.
  • The implementation uses a JSON array (category_tags) on the Record model, which is more efficient than the previous many-to-many association table.

• Category Approval System:

  • A moderation workflow has been introduced. When a user creates a new category, it is marked as "pending" and requires administrator approval to become publicly visible.
  • The Category model is updated with fields to support this workflow, including approved, created_by, and approved_by.
  • Category hierarchy is now supported via a parent_id, allowing for nested category structures.

• API Enhancements:

  • The record creation and update endpoints now accept a list of category_ids.
  • Public API endpoints for categories will only return approved categories.
  • New admin-only endpoints have been added to manage the approval and rejection of pending categories.

• Database Migrations:

  • A new Alembic migration is included to update the database schema with the new fields and relationships.

• Testing:

  • Comprehensive integration tests have been added to validate the new functionality, including CRUD operations for categories, the approval workflow, and associating multiple categories with records.