Saving an attachment (appointment.ics ) adds an extra file extension

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App version

6.901

Where did you get the app from?

F-Droid

Android version

Android 13; Custom Rom: /e/ OS Version 2.1

Device model

Fairphone 3

Steps to reproduce

1. Receive a mail with an attached calendar file (MIME: text/calendar, name for example: appointment.ics)
2. Save the attachment to the filesystem. The filename in the save dialog is correctly shown as appointment.ics

Expected behavior

Search for the file in the file browser and find, that it has been saved as apointment.ics

Actual behavior

Search for the file in the file browser and find, that it has been saved as apointment.ics.txt

Logs

--------- beginning of main
06-21 20:45:24.112 9043 9067 I MessagingController: Running command 'clearNotifications', seq = 841 (foreground priority)
06-21 20:45:24.114 9043 9067 V NotificationController: Removing some notifications for account da64a12f-9663-49f2-9097-d79d92f07dd9
06-21 20:45:24.115 9043 9067 V NotificationController: Removing some notifications for account 582425d0-6f4b-4e9a-ac4b-2a5b2ac58bc5
06-21 20:45:24.115 9043 9067 I MessagingController: Command 'clearNotifications' completed
06-21 20:45:24.127 9043 10368 E OpenGLRenderer: Unable to match the desired swap behavior.
06-21 20:45:28.981 9043 9043 D MessageViewFragment: MessageViewFragment displaying message MessageReference(accountUuid=da64a12f-9663-49f2-9097-d79d92f07dd9, folderId=2, uid=7027)
06-21 20:45:28.987 9043 9043 D MessageLoaderHelper: Creating new local message loader
06-21 20:45:29.014 9043 9043 D MessageLoaderHelper: Creating new decode message loader
06-21 20:45:29.015 9043 8367 V NotificationController: Removing notification for message MessageReference(accountUuid=da64a12f-9663-49f2-9097-d79d92f07dd9, folderId=2, uid=7027)
06-21 20:45:29.187 9043 9043 D Utility : External images found
06-21 20:45:38.135 9043 10368 E OpenGLRenderer: Unable to match the desired swap behavior.
k9-log.txt (END)

Reproduce the issue by saving a text/calendar attachment named appointment.ics on Android, then trace the attachment save flow and filename handling. Verify the saved file keeps its original .ics extension rather than receiving an additional .txt extension.