Revert "fix: 序列号列兜底显示 — external_serial为空时展示身份证后6位"

This reverts commit 8ac4c425a5.

frontend/src/pages/admin/AdminTasksPage.tsx

@@ -404,7 +404,7 @@ export default function AdminTasksPage() {
                         <div key={p.id}>
                           <div className="grid gap-2 border-t border-gray-50 px-5 py-3 items-center text-sm hover:bg-gray-50/50" style={{ gridTemplateColumns: "repeat(16, minmax(0, 1fr))" }}>
                             <div className="col-span-2 font-mono text-xs font-semibold text-gray-800 tracking-wider cursor-pointer hover:text-blue-600 underline decoration-dotted" onClick={() => setQrSerial(p.serial_number)} title="点击查看二维码">{p.serial_number}</div>
-                            <div className="col-span-1 font-mono text-xs text-gray-600 truncate" title={p.external_serial || p.serial_number}>{p.external_serial || (p.serial_number ? "…" + p.serial_number.slice(-6) : "—")}</div>
+                            <div className="col-span-1 font-mono text-xs text-gray-600 truncate">{p.external_serial || "—"}</div>
                             <div className="col-span-2 text-xs text-gray-500 truncate">{p.spec_model || p.material_name || p.material_id || "—"}</div>
                             <div className="col-span-1"><span className="text-xs font-medium text-gray-700">{p.overall_status || "—"}</span></div>
                             <div className="col-span-1"><span className={`inline-flex items-center rounded-full px-2 py-0.5 text-[10px] font-medium ${statusCfg.bg} ${statusCfg.text}`}>{statusCfg.label}</span></div>