feat: invite management API: DELETE /v1/user/invite/:id (204, cancels a pending invite) and POST /v1/user/invite/:id/renew (200, new code, expires_at = now+3d, created_at = now, resends the invitation email, old link dead)

internal/infrastructure/useCases/inviteLookup.go

@@ -0,0 +1,16 @@
+package useCases
+
+import "RenewCMS/internal/domain/invite"
+
+func findManageableInvite(inviteRepository invite.Repository, id uint32) (invite.Invite, error) {
+	for _, existing := range inviteRepository.GetAll() {
+		if existing.ID != id {
+			continue
+		}
+		if existing.AcceptedAt != nil {
+			return invite.Invite{}, invite.ErrInviteAlreadyAccepted
+		}
+		return existing, nil
+	}
+	return invite.Invite{}, invite.ErrInviteNotFound
+}