feat: add cancellable document status (#2992)

Adds a CANCELLED envelope status that privileged members (owner or team
admin/manager) can move a pending document into. Sending recipient
notifications via a background job while retaining the document in the
dashboard as proof of distribution.

Includes a dedicated Cancelled tab, single and bulk cancel actions,
the ENVELOPE_CANCELLED mutability guard, and e2e coverage for
permissions
and visibility.

packages/lib/server-only/admin/get-documents-stats.ts

@@ -18,6 +18,7 @@ export const getDocumentStats = async () => {
     [ExtendedDocumentStatus.PENDING]: 0,
     [ExtendedDocumentStatus.COMPLETED]: 0,
     [ExtendedDocumentStatus.REJECTED]: 0,
+    [ExtendedDocumentStatus.CANCELLED]: 0,
     [ExtendedDocumentStatus.ALL]: 0,
   };