Signal does not accept system drag-and-drop for images between apps

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• This isn't a feature request or a discussion topic

Bug description

On iOS (and more recently on Android) you can hold down on an image in an app like Apple Photos, drag it with one finger, and use another finger to navigate to a different app, such as iMessage, where you can drop the image to paste it. This feature works smoothly across many apps. But unfortunately, it doesn’t work with Signal, even though it shouldn’t be an issue, especially considering Signal is a native Swift app.

Steps to reproduce

1. Open Apple Photos (or any other app that supports drag-and-drop).
2. Tap and hold on an image until it lifts and follows your finger.
3. Use another finger to swipe and navigate to the Signal app (e.g., using the home bar or multitasking view).
4. Open a conversation in Signal where you’d normally send a photo.
5. Drag the image over the message input area or conversation window in Signal.
6. Attempt to drop the image into the conversation.

Actual result: Nothing happens. Signal does not accept the dropped image.

Expected result: The image should be accepted and ready to send in the Signal chat, as it does in other messaging apps like iMessage.

Screenshots

https://github.com/user-attachments/assets/5ed75643-4fdf-4bc3-923d-a884f16258e1

Device info

Device: iPhone 15 Pro Max

iOS version: 18.5

Signal version: 7.62 (817)

Link to debug log

https://debuglogs.org/ios/7.62.0/a789ba4b17695db31ffa8d39988968d85cd6dc74889adc194ce38a5919d31e5f.zip

Start by reproducing the drag-and-drop flow on the reported iPhone and iOS versions, focusing on Signal's conversation message input area. Trace how images dropped from another app are handled and verify that a dropped image becomes ready to send in the chat.