Extends expense entry functionality to support fiat currencies.
Users can now specify a currency (e.g., EUR, USD) when creating expense entries. The specified amount is converted to satoshis using exchange rates. The converted amount and currency information are stored in the journal entry metadata. Also adds an API endpoint to retrieve allowed currencies and updates the UI to allow currency selection when creating expense entries.
Removes the `castle.` prefix from database table names in queries, streamlining data access.
Updates authentication to use `WalletTypeInfo` dependency injection for retrieving wallet information. This improves security and aligns with LNBits' authentication patterns. Also modifies the main router's tag to uppercase.
