Deck Attachment Folder with Hierarchy

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Is your feature request related to a problem? Please describe.
As described in #3239 the files attached to a card are stored in only one Folder. If you upload two files with the same name at different cards the latest file gets renamed with an unnecessary number in brackets. Moreover all files are in one folder which makes it really complex if you have many files attached. If you are a heavy and add only 5 files to the cards per day, the list will get very long fast.

Describe the solution you'd like
Store the files from a card in its own assigned folder. The hierarchy of the deck folder would look like:

• Deck
  --- Card1 Description
  --------Attachment 1
  --------Attachment 2
  --- Card2 Description
  --------Attachment 1
  --------Attachment 2
  --- Card3 Description
  --------Attachment 1
  --------Attachment 2

This would solve the renaming issue and it is an a more uncluttured approach to store the files.

Additional context
If the descritption of the Card is used for the foldernames and the description gets edited it won't match any longer. So it needs to get renamed or we could use the card id for the name of the folder. But this gets confusing for the user too.

No files or tests are named. Start by reading issue #3239 and tracing the existing card-attachment storage entry point; determine how per-card folders should handle renamed card descriptions or stable card IDs. Done means attachments are separated by card, duplicate names no longer require numeric suffixes, and the chosen folder naming remains consistent after edits.