Add contribution payment options to registries

- Added support for single and amount-specific QR codes.
- Updated `RegistrySettings` model and database schema.
- Enhanced `RegistryAdmin` to configure payment options.
- Introduced `RegistryContributionAmount` for partial fulfillment.
- Updated `RegistryPublic` to display contribution progress.
- Added new models for payment methods and QR code handling.
- Improved privacy by limiting contributor visibility.

src/BirthList.Domain/Entities/RegistrySettings.cs

@@ -7,6 +7,8 @@ public class RegistrySettings
     public string? BankAccountBic { get; set; }
     public string? BankAccountDisplayName { get; set; }
     public bool ShowBankAccountName { get; set; }
+    public string? ContributionQrCodeUrl { get; set; }
+    public string? ContributionAmountQrCodesJson { get; set; }
 
     public Registry Registry { get; set; } = null!;
 }