Add upload progress bar with SSE extraction status

ISO uploads now show a progress bar during file transfer (via XHR
upload.onprogress) and real-time extraction status (via SSE events
through the existing Hub). Falls back to plain form POST if JS is
disabled.

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

internal/api/ui.go

@@ -167,34 +167,64 @@ func (u *UI) NewImageForm(w http.ResponseWriter, r *http.Request) {
 }
 
 func (u *UI) UploadImage(w http.ResponseWriter, r *http.Request) {
+	isXHR := r.Header.Get("X-Requested-With") == "XMLHttpRequest"
+
 	if err := r.ParseMultipartForm(0); err != nil {
-		renderHTML(w, imageUploadForm("Invalid form submission"))
+		if isXHR {
+			writeJSON(w, http.StatusBadRequest, map[string]any{"ok": false, "error": "Invalid form submission"})
+		} else {
+			renderHTML(w, imageUploadForm("Invalid form submission"))
+		}
 		return
 	}
 
 	name := strings.TrimSpace(r.FormValue("name"))
 	version := strings.TrimSpace(r.FormValue("version"))
 	kind := strings.TrimSpace(r.FormValue("kind"))
+	uploadID := strings.TrimSpace(r.FormValue("upload_id"))
 
 	file, _, err := r.FormFile("iso")
 	if err != nil {
-		renderHTML(w, imageUploadForm("ISO file is required"))
+		if isXHR {
+			writeJSON(w, http.StatusBadRequest, map[string]any{"ok": false, "error": "ISO file is required"})
+		} else {
+			renderHTML(w, imageUploadForm("ISO file is required"))
+		}
 		return
 	}
 	defer file.Close()
 
+	var progressFn image.ProgressFunc
+	if uploadID != "" {
+		progressFn = func(stage, detail string) {
+			u.Hub.Publish(events.Event{
+				Name:    "image.upload_progress",
+				Payload: fmt.Sprintf(`{"upload_id":%q,"stage":%q,"detail":%q}`, uploadID, stage, detail),
+			})
+		}
+	}
+
 	_, err = u.ImageSvc.Upload(r.Context(), image.UploadParams{
-		Name:    name,
-		Kind:    kind,
-		Version: version,
-		ISO:     file,
+		Name:       name,
+		Kind:       kind,
+		Version:    version,
+		ISO:        file,
+		OnProgress: progressFn,
 	})
 	if err != nil {
-		renderHTML(w, imageUploadForm(err.Error()))
+		if isXHR {
+			writeJSON(w, http.StatusInternalServerError, map[string]any{"ok": false, "error": err.Error()})
+		} else {
+			renderHTML(w, imageUploadForm(err.Error()))
+		}
 		return
 	}
 
-	http.Redirect(w, r, "/images", http.StatusSeeOther)
+	if isXHR {
+		writeJSON(w, http.StatusOK, map[string]any{"ok": true})
+	} else {
+		http.Redirect(w, r, "/images", http.StatusSeeOther)
+	}
 }
 
 func (u *UI) SetDefaultImage(w http.ResponseWriter, r *http.Request) {