add csfloat api usage

BlueLaminate/BlueLaminate.EFCore/Configurations/ListingConfiguration.cs

@@ -0,0 +1,43 @@
+using BlueLaminate.EFCore.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace BlueLaminate.EFCore.Configurations;
+
+public class ListingConfiguration : IEntityTypeConfiguration<Listing>
+{
+    public void Configure(EntityTypeBuilder<Listing> entity)
+    {
+        // CSFloat's listing id is the natural key; the incremental sweep upserts
+        // against it and must never create duplicates.
+        entity.HasIndex(e => e.CsFloatListingId).IsUnique();
+
+        entity.Property(e => e.Price).HasPrecision(18, 2);
+        // Full precision to match SkinInstance for exact fingerprint joins.
+        entity.Property(e => e.FloatValue).HasColumnType("numeric(20,18)");
+
+        // Store the enum as text so the DB is self-describing (matches the
+        // project's readable-data leaning over opaque ints).
+        entity.Property(e => e.Status).HasConversion<string>();
+
+        // The sweep filters/sorts by item identity and by what's still active.
+        entity.HasIndex(e => new { e.DefIndex, e.PaintIndex });
+        entity.HasIndex(e => e.Status);
+
+        // Best-effort catalogue link: a global sweep sees items we may not have,
+        // so the FK is optional and set null if the skin is later removed.
+        entity.HasOne(e => e.Skin)
+            .WithMany()
+            .HasForeignKey(e => e.SkinId)
+            .OnDelete(DeleteBehavior.SetNull);
+
+        // Listings roll up to the physical item they represent.
+        entity.HasOne(e => e.SkinInstance)
+            .WithMany(i => i.Listings)
+            .HasForeignKey(e => e.SkinInstanceId)
+            .OnDelete(DeleteBehavior.SetNull);
+
+        // Dupe analysis groups a fingerprint's listings by asset id.
+        entity.HasIndex(e => e.AssetId);
+    }
+}