feat: add image management functionality

- Implemented image folder repository with CRUD operations.
- Added image reference repository for managing image references to articles.
- Created image repository for handling image assets, including listing, inserting, updating, and deleting images.
- Introduced image usage repository to track storage usage and quotas for tenants.
- Added SQL queries for image assets, folders, references, and usage.
- Developed image handler for HTTP endpoints to manage images and folders.
- Created database migration scripts for image-related tables and structures.

server/migrations/20260415100000_create_image_tables.down.sql

@@ -0,0 +1,8 @@
+DROP TABLE IF EXISTS image_asset_references;
+DROP TABLE IF EXISTS image_assets;
+DROP TABLE IF EXISTS image_folders;
+DROP TABLE IF EXISTS tenant_image_storage_usage;
+
+UPDATE plans
+SET quota_policy_json = quota_policy_json - 'image_storage_bytes'
+WHERE deleted_at IS NULL;