Restructure web UI navigation into 7 numbered workflow stages

Replace the flat menu (Dashboard, Audit, Validate, Burn, Benchmark,
Tasks, Tools) with a numbered progression that guides engineers through
a logical acceptance workflow:

  Dashboard (landing) → 1. Audit → 2. Check → 3. Load → 4. Speed
  → 5. Endurance → 6. Tools → 7. Settings

Key changes:
- layout.go: numbered nav labels, new hrefs, Tasks removed from nav
  and replaced with a persistent sidebar badge (polls /api/tasks every
  5 s, highlights amber when tasks are active)
- server.go: 301 redirects from /validate→/check, /burn→/load,
  /benchmark→/speed for backward compatibility
- pages.go: dispatch cases for all new routes; old routes kept as
  fallbacks
- page_validate.go: add renderCheck() — non-destructive check page
  with validate-mode tests only (no stress toggle, no targeted-stress/
  targeted-power/pulse cards)
- page_burn.go: add renderLoad() wrapper; update scope alert to
  reference /check instead of /validate
- page_benchmark.go: add renderSpeed() (performance focus) and
  renderEndurance() (stability/overnight focus) wrappers
- page_settings.go: new Settings page with blackbox logging toggle,
  NVIDIA driver reset, and build info
- server_test.go: update five tests to use new route names and
  content expectations

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

audit/internal/webui/server.go

@@ -1419,13 +1419,16 @@ func (h *handler) handlePage(w http.ResponseWriter, r *http.Request) {
 	if page == "" {
 		page = "dashboard"
 	}
-	// Redirect old routes to new names
+	// Redirect legacy routes to new named pages
 	switch page {
-	case "tests":
-		http.Redirect(w, r, "/validate", http.StatusMovedPermanently)
+	case "validate", "tests":
+		http.Redirect(w, r, "/check", http.StatusMovedPermanently)
 		return
-	case "burn-in":
-		http.Redirect(w, r, "/burn", http.StatusMovedPermanently)
+	case "burn", "burn-in":
+		http.Redirect(w, r, "/load", http.StatusMovedPermanently)
+		return
+	case "benchmark":
+		http.Redirect(w, r, "/speed", http.StatusMovedPermanently)
 		return
 	}
 	body := renderPage(page, h.opts)