Add download all attachments to messages.

[RubenGarcia]

docs: Document additional packages needed in ubuntu
fix: Changes to save multiple attachments in same message with a different name.

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Description

This merge request builds on
#2917
(https://github.com/oxen-io/session-desktop-temp/issues/228)
and adds the possibility to download all attachments to a directory in one go.

[Bilb]

Hey, could we instead of relying on those chrome experimental features,

• show a picker to choose the folder,
• get the full path of that folder,
• send that folder, a Array<{filename:string, plaintext: Uint8Array} to the main side of electron and have it create the files and fill the content of it?

[RubenGarcia]

Hey, could we instead of relying on those chrome experimental features,

* show a picker to choose the folder,

* get the full path of that folder,

* send that folder, a Array<{filename:string, plaintext: Uint8Array} to the main side of electron and have it create the files and fill the content of it?

The last part I don't know how to do.
I only activate the experimental features so I have access to the functions which save to disk in the background. I suppose they be available without enabling experimental once electron is updated, so we can wait until then and remove the line that enables experimental features.

[Bilb]

ok, I'll mark this PR as draft until then

[RubenGarcia]

v25.8.4 still needs the request for experimental features.

[KeeJef]

To ensure I understand correctly, this feature allows users to download all attachments of a message by selecting an option from the context menu that appears when clicking on a message with multiple attachments. Does this action prompt the user to choose a save location via a file picker, or are the attachments automatically saved to a default location?

Does this still rely on Chrome experimental features?

[RubenGarcia]

It asks the user to select a directory.
I think the feature is still marked as experimental, but I have not checked lately.