Cascade, Orphan Removal & Soft Delete

`CascadeType.ALL` propagates the parent's operations to children; `orphanRemoval` deletes a child when it is removed from the parent's collection.

Soft delete marks a row as deleted instead of removing it; `@SQLDelete` turns DELETE into UPDATE, `@SQLRestriction` auto-filters queries, `@Filter` is a dynamic toggle, and `@SoftDelete` does it all in one annotation.