Adds a metadata column to the entry_lines table.
This column will store currency conversion data as JSON, allowing for future flexibility in handling different types of metadata.
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." schema prefix from database table creation and index definitions in the migration file.
This change enhances database portability by allowing the application to function correctly with different database configurations.
