Enhance file download handling and web interface. Update the download handler to support inline previews based on query parameters. Introduce a preview button for supported file types in the web interface, along with corresponding styles for action buttons. This improves user experience by allowing direct file previews without downloads.

lib/agent/handlers.go

@@ -172,7 +172,11 @@ func (a *Agent) handleDownload(w http.ResponseWriter, r *http.Request) {
 		_, _ = f.Seek(0, io.SeekStart)
 	}
 	w.Header().Set("Content-Type", contentType)
-	w.Header().Set("Content-Disposition", `attachment; filename="`+strings.ReplaceAll(name, `"`, "'")+`"`)
+	disp := "attachment"
+	if r.URL.Query().Get("inline") == "1" {
+		disp = "inline"
+	}
+	w.Header().Set("Content-Disposition", disp+`; filename="`+strings.ReplaceAll(name, `"`, "'")+`"`)
 	w.Header().Set("Accept-Ranges", "bytes")
 	http.ServeContent(w, r, name, info.ModTime(), f)
 }