fix(webui): build support bundle synchronously on download, bypass task queue

Support bundle is now built on-the-fly when the user clicks the button,
regardless of whether other tasks are running:

- GET /export/support.tar.gz builds the bundle synchronously and streams it
  directly to the client; the temp archive is removed after serving
- Remove POST /api/export/bundle and handleAPIExportBundle — the task-queue
  approach meant the bundle could only be downloaded after navigating away
  and back, and was blocked entirely while a long SAT test was running
- UI: single "Download Support Bundle" button; fetch+blob gives a loading
  state ("Building...") while the server collects logs, then triggers the
  browser download with the correct filename from Content-Disposition

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

audit/internal/webui/server.go

@@ -261,7 +261,6 @@ func NewHandler(opts HandlerOptions) http.Handler {
 
 	// Export
 	mux.HandleFunc("GET /api/export/list", h.handleAPIExportList)
-	mux.HandleFunc("POST /api/export/bundle", h.handleAPIExportBundle)
 	mux.HandleFunc("GET /api/export/usb", h.handleAPIExportUSBTargets)
 	mux.HandleFunc("POST /api/export/usb/audit", h.handleAPIExportUSBAudit)
 	mux.HandleFunc("POST /api/export/usb/bundle", h.handleAPIExportUSBBundle)
@@ -386,15 +385,12 @@ func (h *handler) handleRuntimeHealthJSON(w http.ResponseWriter, r *http.Request
 }
 
 func (h *handler) handleSupportBundleDownload(w http.ResponseWriter, r *http.Request) {
-	archive, err := app.LatestSupportBundlePath()
+	archive, err := app.BuildSupportBundle(h.opts.ExportDir)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) {
-			http.Error(w, "support bundle not built yet", http.StatusNotFound)
-			return
-		}
-		http.Error(w, fmt.Sprintf("locate support bundle: %v", err), http.StatusInternalServerError)
+		http.Error(w, fmt.Sprintf("build support bundle: %v", err), http.StatusInternalServerError)
 		return
 	}
+	defer os.Remove(archive)
 	w.Header().Set("Cache-Control", "no-store")
 	w.Header().Set("Content-Type", "application/gzip")
 	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", filepath.Base(archive)))