Add power results table, fix benchmark results refresh, bound memtester

- Benchmark page now shows two result sections: Performance (scores) and
  Power / Thermal Fit (slot table). After any benchmark task completes
  the results section auto-refreshes via GET /api/benchmark/results
  without a full page reload.
- Power results table shows each GPU slot with nominal TDP, achieved
  stable power limit, and P95 observed power. Rows with derated cards
  are highlighted amber so under-performing slots stand out at a glance.
  Older runs are collapsed in a <details> summary.
- memtester is now wrapped with timeout(1) so a stuck memory controller
  cannot cause Validate Memory to hang indefinitely. Wall-clock limit is
  ~2.5 min per 100 MB per pass plus a 2-minute buffer.

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

audit/internal/webui/api.go

@@ -1529,6 +1529,11 @@ func (h *handler) handleAPINetworkRollback(w http.ResponseWriter, _ *http.Reques
 	writeJSON(w, map[string]string{"status": "rolled back"})
 }
 
+func (h *handler) handleAPIBenchmarkResults(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	fmt.Fprint(w, renderBenchmarkResultsCard(h.opts.ExportDir))
+}
+
 func (h *handler) rollbackPendingNetworkChange() error {
 	h.pendingNetMu.Lock()
 	pnc := h.pendingNet