feat(upload): add transfer rate tracking and 6-hour expiry option

- Implement real-time transfer rate tracking and display upload speed (e.g., Mb/s) in the progress status.
- Add a 6-hour (360 minutes) option to the upload expiry selection ladder.
- Fix an issue where the "new upload" button remained visible by explicitly toggling its display style and adding a CSS fallback for the `hidden` attribute.

backend/libs/handlers/pages.go

@@ -95,7 +95,7 @@ func (a *App) homeExpiryOptions(settings services.UploadPolicySettings, user ser
 }
 
 func buildExpiryOptions(maxDays int, unlimited bool) ([]expiryOption, int) {
-	ladder := []int{60, 720, 1440, 2880, 4320, 7200, 10080, 14400, 20160, 43200, 86400, 129600, 259200, 525600}
+	ladder := []int{60, 360, 720, 1440, 2880, 4320, 7200, 10080, 14400, 20160, 43200, 86400, 129600, 259200, 525600}
 
 	capMinutes := maxDays * 24 * 60
 	if unlimited || capMinutes <= 0 {