iOS: Audio messages, file attachments, and caching

The iOS app now handles rich media natively. Record audio, send files, and pick up conversations on your Mac with Handoff.

What's new

• Record and send audio messages with a waveform playback UI.
• Send file attachments directly in chat with an attachment grid for multiple files.
• Three-layer caching for images, link previews, and messages so the app stays fast offline.
• Apple Handoff lets you start a conversation on your phone and pick it up on your Mac.
• Swipe-to-reply, emoji reactions, date headers, and in-conversation search.
• Optimized for both iPhone and iPad layouts.