Fix #706: Use SeedCodec.encodeSeed() in Seed.java instead of direct AddressBase58.encode()

Replace direct AddressBase58.encode() calls in ed25519SeedFromEntropy() and
secp256k1SeedFromEntropy() with SeedCodec.getInstance().encodeSeed(), centralizing
seed encoding logic in SeedCodec to match the existing pattern used for decoding.
Remove now-unused imports (AddressBase58, Lists, UnsignedInteger).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: utafrali

xrpl4j-core/src/main/java/org/xrpl/xrpl4j/crypto/keys/Seed.java

@@ -22,15 +22,12 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
-import com.google.common.collect.Lists;
 import com.google.common.hash.Hashing;
-import com.google.common.primitives.UnsignedInteger;
 import org.bouncycastle.asn1.sec.SECNamedCurves;
 import org.bouncycastle.asn1.x9.X9ECParameters;
 import org.bouncycastle.crypto.params.ECDomainParameters;
 import org.bouncycastle.crypto.params.Ed25519PrivateKeyParameters;
 import org.bouncycastle.crypto.params.Ed25519PublicKeyParameters;
-import org.xrpl.xrpl4j.codec.addresses.AddressBase58;
 import org.xrpl.xrpl4j.codec.addresses.Base58;
 import org.xrpl.xrpl4j.codec.addresses.Decoded;
 import org.xrpl.xrpl4j.codec.addresses.KeyType;
@@ -126,13 +123,9 @@ static Seed ed25519Seed() {
   static Seed ed25519SeedFromEntropy(final Entropy entropy) {
     Objects.requireNonNull(entropy);
 
-    final String base58EncodedSeed = AddressBase58.encode(
-      entropy.value(),
-      Lists.newArrayList(Version.ED25519_SEED),
-      UnsignedInteger.valueOf(entropy.value().length())
-    );
+    final String base58EncodedSeed = SeedCodec.getInstance().encodeSeed(entropy.value(), KeyType.ED25519);
 
-    return new DefaultSeed(UnsignedByteArray.of(AddressBase58.decode(base58EncodedSeed)));
+    return new DefaultSeed(UnsignedByteArray.of(Base58.decode(base58EncodedSeed)));
   }
 
   /**
@@ -155,11 +148,7 @@ static Seed secp256k1Seed() {
   static Seed secp256k1SeedFromEntropy(final Entropy entropy) {
     Objects.requireNonNull(entropy);
 
-    final String base58EncodedSeed = AddressBase58.encode(
-      entropy.value(),
-      Lists.newArrayList(Version.FAMILY_SEED),
-      UnsignedInteger.valueOf(entropy.value().length())
-    );
+    final String base58EncodedSeed = SeedCodec.getInstance().encodeSeed(entropy.value(), KeyType.SECP256K1);
 
     return new DefaultSeed(UnsignedByteArray.of(Base58.decode(base58EncodedSeed)));
   }