Cards: 3x2 front/back sprites, appearance overlays, flip via the Toggle menu

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Decentralized.Domain/Mining.cs

@@ -84,6 +84,8 @@ namespace Decentralized.Domain
         public double Health = 100;
         public bool Dead;
         public bool Refurbished;
+        /// <summary>外观；新卡（正规渠道）没有记录，按全新画。</summary>
+        public CardLook Look;
 
         public HardwareSpec Label => Hardware.Specs[Model];
         public HardwareSpec Chip => Hardware.Specs[FakeOf ?? Model];