fix(frontend): iOS clipboard paste handling for text and images

[namanrajpal]

Summary

Fixes clipboard paste behavior on iOS Safari by properly detecting text vs image content and allowing the browser to handle text paste natively.

Problem

On iOS Safari/Chrome, the synchronous event.clipboardData API doesn't reliably expose image content. The async Clipboard API (navigator.clipboard.read()) is required for reading images, but calling event.preventDefault() unconditionally breaks normal text pasting.

Solution

Implemented a two-phase paste detection for iOS:

1. Text check first: Attempt to read text via navigator.clipboard.readText()

   • If text exists → early return to let browser handle text paste natively
   • If no text or read fails → proceed to image handling

2. Image handling: Only preventDefault() and use async Clipboard API when clipboard doesn't contain text

Changes

• frontend/src/components/message/PromptInput.tsx: Added iOS-specific paste detection logic that preserves native text paste behavior while enabling image paste via async Clipboard API

Testing

• Verified text paste works on iOS Safari
• Verified image paste works on iOS Safari
• Verified existing paste behavior unchanged on desktop browsers

[oneishaansharma]

Thanks for the improvement. I also noticed another bug where pressing "enter" or "return" key in Safari on iOS keyboard behaves inconsistently. i.e. sometimes it adds next line char (usually the first time - leading to sending a message before I'm ready), and others it "sends" the message. Only mentioning since you're likely in the same area.