feat(db): add deletedAt audit timestamp to soft-deletable models

Add deletedAt DateTime? to User, Client, Role, Resource, and Blueprint
models for GDPR-compliant deactivation audit trail. Soft-delete mutations
now stamp deletedAt: new Date() on deactivation and clear it on
reactivation. Migration and test assertions updated accordingly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/api/src/router/role-procedure-support.ts

@@ -247,7 +247,7 @@ export async function deactivateRole(
   const role = await ctx.db.$transaction(async (tx) => {
     const result = await tx.role.update({
       where: { id: input.id },
-      data: { isActive: false },
+      data: { isActive: false, deletedAt: new Date() },
       include: { _count: { select: { resourceRoles: true } } },
     });