Adds the ability to read and write to amiibo bin files (#348)

This introduces the ability to read and write game data and model
information from an Amiibo dump file (BIN format). Note that this
functionality requires the presence of a key_retail.bin file. For the
option to appear and function in the UI, ensure that the key_retail.bin
file is located in the <RyujinxData>/system folder.

src/Ryujinx.HLE/HOS/Services/Nfc/AmiiboDecryption/AmiiboDecrypter.cs

@@ -0,0 +1,43 @@
+using System.IO;
+
+namespace Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption
+{
+    public class AmiiboDecrypter
+    {
+        public AmiiboMasterKey DataKey { get; private set; }
+        public AmiiboMasterKey TagKey { get; private set; }
+
+        public AmiiboDecrypter(string keyRetailBinPath)
+        {
+            var combinedKeys = File.ReadAllBytes(keyRetailBinPath);
+            var keys = AmiiboMasterKey.FromCombinedBin(combinedKeys);
+            DataKey = keys.DataKey;
+            TagKey = keys.TagKey;
+        }
+
+        public AmiiboDump DecryptAmiiboDump(byte[] encryptedDumpData)
+        {
+            // Initialize AmiiboDump with encrypted data
+            AmiiboDump amiiboDump = new AmiiboDump(encryptedDumpData, DataKey, TagKey, isLocked: true);
+
+            // Unlock (decrypt) the dump
+            amiiboDump.Unlock();
+
+            // Optional: Verify HMACs
+            amiiboDump.VerifyHMACs();
+
+            return amiiboDump;
+        }
+
+        public AmiiboDump EncryptAmiiboDump(byte[] decryptedDumpData)
+        {
+            // Initialize AmiiboDump with decrypted data
+            AmiiboDump amiiboDump = new AmiiboDump(decryptedDumpData, DataKey, TagKey, isLocked: false);
+
+            // Lock (encrypt) the dump
+            amiiboDump.Lock();
+
+            return amiiboDump;
+        }
+    }
+}