Improve upload feedback and background uploading for media in the app

Context:
When uploading images or videos in the Oneteam app, there is little to no visible feedback about upload progress, and the user cannot continue using the app until the upload completes. This creates uncertainty about whether the upload is working and interrupts the workflow.

Desired solution:

• Show the media inline in the chat or post immediately after selecting it, with a visible upload progress indicator overlaid on the preview (similar to WhatsApp)

• Allow the upload to continue in the background so users can keep using the app while the file is being sent

• On iOS specifically: replace the generic spinning circle with more descriptive progress states (e.g. "Uploading… Processing… Sending")

Current behavior:

• iOS: a spinning circle is shown with no further context, it is unclear whether the upload is progressing or stuck

• Android: progress states are described ("Uploading / Processing / Sending"), which is better.

• The uploaded media does not appear in the conversation until the upload is fully complete