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.Infrastructure/Persistence/RegistryDbContext.cs

@@ -57,6 +57,8 @@ public class RegistryDbContext(DbContextOptions<RegistryDbContext> options) : Db
             entity.Property(x => x.BankAccountIban).HasMaxLength(34);
             entity.Property(x => x.BankAccountBic).HasMaxLength(11);
             entity.Property(x => x.BankAccountDisplayName).HasMaxLength(120);
+            entity.Property(x => x.ContributionQrCodeUrl).HasMaxLength(2048);
+            entity.Property(x => x.ContributionAmountQrCodesJson).HasMaxLength(4000);
             entity.HasOne(x => x.Registry)
                 .WithOne()
                 .HasForeignKey<RegistrySettings>(x => x.RegistryId)