Attachment collapse state is not persisted when switching channels

Description:

When a user collapses a message attachment (image/GIF), that collapsed state is not persisted. Switching to another channel and returning re-mounts the message and the attachment renders expanded again. The user's interaction (collapse) is forgotten on every channel switch.

Steps to reproduce:

Post a message with an image or GIF attachment in a channel.
Click the collapse arrow on the attachment to hide its content.
Switch to another channel.
Switch back to the original channel.
Expected behavior:

Attachment remains collapsed across channel switches — the user's manual collapse persists at least for the duration of the session.

Actual behavior:

Attachment is expanded again on return. The user must re-collapse it every time they navigate back to the channel.

Server Setup Information:

Version of Rocket.Chat Server: 8.1.1
Client Setup Information:

Desktop App or Browser Version: [fyll i, t.ex. Chrome 130]
Operating System: Windows 11
Additional context:

Affects channels with frequent media attachments. Users want to collapse media to reduce visual noise without permanently hiding it for everyone, but currently have to re-collapse every time they revisit the channel — high friction.

Suggested fix: persist per-user, per-message UI state for collapsed (e.g., localStorage keyed on message ID + user ID, or session-scoped).

Start by reproducing the issue with an image or GIF attachment: collapse it, switch channels, and return to confirm the state is lost. Trace the attachment collapse UI and its state across the channel remount; done means the user's collapsed state remains for the session when returning to the channel without hiding the attachment permanently.