Add Option to Enter Amounts in EUR or Sats (for Sending & Receiving)

In both the Send Bitcoin and Receive flows, Bringin LN Wallet currently only allows users to input amounts in sats.

This creates friction for euro-based users who want to send or request a specific euro value (e.g. “€20 worth of Bitcoin”).

Adding a currency toggle (EUR ⇄ sats) across both flows would make the app more intuitive and aligned with everyday user behavior.