Release v2.1.6: Balance card UI, smart send button, and co-signing fixes

[boldbitcoin]

Release v2.1.6

🎨 UI Improvements

• Balance Card in Send Modal: New prominent balance card displayed above amount input
  • Shows available balance in BTC and fiat currency
  • Integrated "Max" button for quick balance selection
  • Clean, professional UI with card styling

✨ New Features

• Smart Balance Check for Send Button: Automatic balance refresh when clicking Send with zero balance
  • Prevents modal from opening prematurely when balance hasn't loaded
  • Shows loading spinner on Send button during balance check
  • Automatically opens modal if balance is found, or shows alert if truly zero
  • Prevents multiple rapid clicks with button disable state
  • 5-second timeout with graceful error handling

🐛 Bug Fixes

• Co-signing Go Panic Recovery: Fixed potential panic crashes in Nostr transport layer during co-signing

  • Added panic recovery with stack trace logging in Client.Publish goroutine
  • Improved nil pointer safety when extracting relay URLs
  • Better error messages for debugging relay connection issues
  • Enhanced resiliency for co-signing message delivery across multiple relays

• Send Button Balance Race Condition: Fixed issue where Send button would show "Insufficient Balance" alert even when balance was still loading

  • Eliminates flickering and need to click Send button multiple times
  • Better UX with immediate feedback during balance check

📝 Changes

• Send Modal UI Enhancement: Improved balance visibility and Max button placement
  • Balance card replaces inline "Max" text link
  • More prominent balance display with better visual hierarchy
  • Updated QR scanner icon to use scan-icon.png for consistency

📦 Technical Details

• WalletHome.tsx: Added checkBalanceForSend() function for dedicated balance fetching
• SendBitcoinModal.tsx: New balance card component with integrated Max button
• client.go: Enhanced panic recovery and error handling in Nostr publish operations
• Error Handling: Improved timeout and error recovery for balance checks

[kar1timmins]

LGTM