Fix attachment loss when switching conversations on mobile web

[exedev-shelley]

Author: momentaryblip
Channel: #shelley
Link: https://discord.com/channels/1405685085923049482/1450334528210993295/1549495790878195723

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Description

On mobile web (Android 14.x Chrome), when a user attaches a file to a conversation and then toggles to another conversation before submitting, the attachment is lost when toggling back to the original conversation.

Context

This was reported for mobile web specifically. Desktop behavior is unknown and should be tested.

Steps to Reproduce

1. Open a conversation on mobile web
2. Attach a file (e.g., PNG image)
3. Before submitting, switch to another conversation
4. Toggle back to the original conversation
5. Observe that the attachment is no longer present

Environment

• Platform: Mobile web
• OS: Android 14.x
• Browser: Chrome

[minikomi]

Confirmed also present on desktop

[philz]

Fixed in f6f46be: unsent attachments are now preserved per conversation across navigation, including uploads that finish after switching away.