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/internal/tenant/repository/queries/image_usage.sql

@@ -0,0 +1,15 @@
+-- name: EnsureImageStorageUsageRow :exec
+INSERT INTO tenant_image_storage_usage (tenant_id, used_bytes)
+VALUES (sqlc.arg(tenant_id), 0)
+ON CONFLICT (tenant_id) DO NOTHING;
+
+-- name: GetImageStorageUsage :one
+SELECT used_bytes, updated_at
+FROM tenant_image_storage_usage
+WHERE tenant_id = sqlc.arg(tenant_id);
+
+-- name: ReleaseImageStorageQuota :exec
+UPDATE tenant_image_storage_usage
+SET used_bytes = GREATEST(0, used_bytes - sqlc.arg(release_bytes)),
+    updated_at = NOW()
+WHERE tenant_id = sqlc.arg(tenant_id);