Reordering template sub-schemas

**Job Story**

When _building or editing a schema template that represents a full form (e.g., "VCS Project Description v5.0a") made up of multiple sub-schemas_, I want _the template to act as a parent/verifiable credential (VC) structure where I can order and organize its sub-schemas from the main screen_, so I can _control the sequence in which sub-schemas appear and ensure the template accurately represents the full form as a single cohesive VC._

**Acceptance Criteria**

* A schema template can contain multiple sub-schemas nested under it
* The template functions as a parent VC structure, with the template itself (e.g., "VCS Project Description v5.0a") representing the overall credential
* Users can reorder sub-schemas within a template from the main screen (e.g., drag-and-drop)
* The order set by the user is saved and reflected wherever the template or its sub-schemas are rendered or issued
* Existing templates with sub-schemas retain their current order by default until manually changed (no unintended reordering on rollout)
* When a schema template is applied to a policy, users can still go to the Manage Schemas tab and create a separate parent schema that references multiple VCs/schema templates (e.g., a parent schema referencing both VCS Project Description v5.0a and v5.0b)

**Artifacts & Considerations**

* Clarify distinction between: (1) a schema template applied directly to a policy, and (2) a parent schema in Manage Schemas that references multiple schema templates/VCs (e.g., v5.0a and v5.0b) as a higher-level grouping
* Consider how schemas created in the Schema Templates are tagged or labeled in the Manage Schemas UI to help differentiate a policy schema from a template schema when they're all merged