feat(preview): add archive listing and browser support

Introduces the ability to browse and preview the contents of archive files directly within the web interface.

Changes include:
- Added a new API endpoint `GET /d/{boxID}/archive/{fileID}` to fetch archive listings.
- Implemented on-demand archive listing generation in the backend.
- Updated the frontend preview component to support rendering and navigating archive contents.

backend/libs/handlers/download.go

@@ -48,8 +48,10 @@ type fileView struct {
 	DownloadURL  string
 	ThumbnailURL string
 	SceneURL     string
+	ArchiveURL   string
 	HasThumbnail bool
 	HasScene     bool
+	HasArchive   bool
 	IconURL      string
 	IconRetroURL string
 	ReactURL     string
@@ -384,6 +386,51 @@ func (a *App) VideoScenesPreview(w http.ResponseWriter, r *http.Request) {
 	http.ServeContent(w, r, file.ID+"-scenes.jpg", object.ModTime, readSeekCloser(object.Body))
 }
 
+func (a *App) ArchiveListing(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("X-Robots-Tag", "noindex, nofollow, noarchive")
+	box, file, ok := a.loadFileForRequest(w, r)
+	if !ok {
+		return
+	}
+	if !jobs.NeedsArchiveListing(file) {
+		http.NotFound(w, r)
+		return
+	}
+	if a.uploadService.IsProtected(box) && box.Obfuscate && !a.isBoxUnlocked(r, box) {
+		http.Error(w, "password required", http.StatusUnauthorized)
+		return
+	}
+
+	if strings.ToLower(filepath.Ext(file.ArchiveListing)) != ".json" {
+		if listing := a.generateMissingArchiveListingForRequest(r, box, file); listing != "" {
+			file.ArchiveListing = listing
+			file.ArchiveListingObjectKey = ""
+		}
+	}
+
+	object, err := a.uploadService.OpenArchiveListingObject(r.Context(), box, file)
+	if err != nil {
+		if listing := a.generateMissingArchiveListingForRequest(r, box, file); listing != "" {
+			file.ArchiveListing = listing
+			file.ArchiveListingObjectKey = ""
+			object, err = a.uploadService.OpenArchiveListingObject(r.Context(), box, file)
+			if err == nil {
+				defer object.Body.Close()
+				w.Header().Set("Content-Type", "application/json")
+				w.Header().Set("Cache-Control", "public, max-age=604800, immutable")
+				http.ServeContent(w, r, file.ID+"-archive.json", object.ModTime, readSeekCloser(object.Body))
+				return
+			}
+		}
+		http.Error(w, "archive preview unavailable", http.StatusInternalServerError)
+		return
+	}
+	defer object.Body.Close()
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Cache-Control", "public, max-age=604800, immutable")
+	http.ServeContent(w, r, file.ID+"-archive.json", object.ModTime, readSeekCloser(object.Body))
+}
+
 func (a *App) generateMissingThumbnailForRequest(r *http.Request, box services.Box, file services.File) string {
 	if file.Thumbnail != "" || !jobs.NeedsThumbnail(file) {
 		return ""
@@ -432,6 +479,31 @@ func (a *App) generateMissingVideoScenesForRequest(r *http.Request, box services
 	return scene
 }
 
+func (a *App) generateMissingArchiveListingForRequest(r *http.Request, box services.Box, file services.File) string {
+	if strings.ToLower(filepath.Ext(file.ArchiveListing)) == ".json" || !jobs.NeedsArchiveListing(file) {
+		return ""
+	}
+	listing, err := jobs.GenerateArchiveListingForFile(a.uploadService, box, file)
+	if err != nil || listing == "" {
+		if err != nil {
+			a.logger.Warn("on-demand archive listing generation failed", withRequestLogAttrs(r, "source", "thumbnail", "severity", "warn", "code", 4108, "box_id", box.ID, "file_id", file.ID, "error", err.Error())...)
+		}
+		return ""
+	}
+	for i := range box.Files {
+		if box.Files[i].ID == file.ID {
+			box.Files[i].ArchiveListing = listing
+			box.Files[i].ArchiveListingObjectKey = ""
+			break
+		}
+	}
+	if err := a.uploadService.SaveBox(box); err != nil {
+		a.logger.Warn("on-demand archive listing metadata save failed", withRequestLogAttrs(r, "source", "thumbnail", "severity", "warn", "code", 4109, "box_id", box.ID, "file_id", file.ID, "error", err.Error())...)
+		return ""
+	}
+	return listing
+}
+
 // servePlaceholderThumbnail serves the fallback image with no-store so the
 // browser re-requests on the next load and picks up the real thumbnail as soon
 // as it has been generated.
@@ -577,8 +649,10 @@ func (a *App) fileViewWithReactions(box services.Box, file services.File, reacti
 		DownloadURL:  fmt.Sprintf("/d/%s/f/%s/download", box.ID, file.ID),
 		ThumbnailURL: fmt.Sprintf("/d/%s/thumb/%s", box.ID, file.ID),
 		SceneURL:     fmt.Sprintf("/d/%s/scene/%s", box.ID, file.ID),
+		ArchiveURL:   fmt.Sprintf("/d/%s/archive/%s", box.ID, file.ID),
 		HasThumbnail: file.Thumbnail != "" || jobs.NeedsThumbnail(file),
 		HasScene:     file.SceneThumbnail != "" || jobs.NeedsVideoScenes(file),
+		HasArchive:   file.ArchiveListing != "" || jobs.NeedsArchiveListing(file),
 		IconURL:      fileIconURL("standard", icon.Standard),
 		IconRetroURL: fileIconURL("retro", icon.Retro),
 		ReactURL:     fmt.Sprintf("/d/%s/f/%s/react", box.ID, file.ID),