fix(backup): order the source aliases a deleted document's keys are read from

The backup export is totally ordered so two exports of the same account are
byte-identical; the alias relation the import-key ledger reads was the one
nested read without an order.

src/lib/documents/tombstones.ts

@@ -45,6 +45,8 @@ export const SOURCE_KEY_SELECT = {
   sourceId: true,
   sourceInstance: true,
   sourceAliases: {
+    // The backup reads through this select, and its export is totally ordered.
+    orderBy: [{ createdAt: "asc" }, { id: "asc" }],
     select: { sourceSystem: true, sourceId: true, sourceInstance: true },
   },
 } as const;