feat(tier): Erwerb/Kauf je Tier (Datum, Preis, Notiz)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

GerbilManagerWebAPI/Migrations/ApplicationContextModelSnapshot.cs

@@ -21,6 +21,38 @@ namespace GerbilManagerWebAPI.Migrations
 
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
 
+            modelBuilder.Entity("GerbilManagerWebAPI.Models.AcquisitionRecord", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateOnly?>("Date")
+                        .HasColumnType("date");
+
+                    b.Property<Guid?>("GerbilId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Note")
+                        .HasColumnType("text");
+
+                    b.Property<decimal?>("Price")
+                        .HasPrecision(10, 2)
+                        .HasColumnType("numeric(10,2)");
+
+                    b.Property<Guid?>("SourceContactId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("GerbilId");
+
+                    b.ToTable("AcquisitionRecords");
+                });
+
             modelBuilder.Entity("GerbilManagerWebAPI.Models.Block", b =>
                 {
                     b.Property<Guid>("Id")