feat: add real-time Soroban token transfer system with Freighter wallet and socket chat sync

[V1ctor-o]

Summary

This PR introduces a full in-chat token transfer system powered by Soroban smart contracts and Freighter wallet integration, with real-time synchronization via Socket.io.

Users can now send tokens directly inside chat messages, with transactions executed on-chain and shared instantly across all connected clients.

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🚀 Features Implemented

💸 Token Transfer Flow

• Added coin icon button in MessageInput
• Popover UI for:
  • Amount input
  • Auto-filled recipient
• Validation ensures amount > 0

🔐 Wallet Integration

• Integrated Freighter wallet signing flow
• Users approve transactions directly from Freighter extension

⛓️ Soroban Smart Contract Execution

• Built Soroban token_transfer transaction flow
• Transaction is simulated and submitted via Stellar SDK
• Transaction hash returned on success

⚡ Real-Time Messaging (Socket.io)

• Transfer messages emitted via socket after success
• Backend persists and broadcasts messages to all connected clients
• Chat updates instantly across users

Closes #31

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