refactor(logging): remove constructor logging from low-level key classes

Medium-priority logging improvements per Clean Code Chapter 3 (Functions):

1. Removed constructor logging from PrivateKey class
   - Removed "Created private key from byte array" debug log
   - Removed "Created private key from hex string" debug log
   - Removed "Generated new random private key" debug log
   - Simplified generateRandomPrivKey() to single return statement

2. Removed constructor logging from PublicKey class
   - Removed "Created public key from byte array" debug log
   - Removed "Created public key from hex string" debug log

3. Removed routine operation logging from BaseKey class
   - Removed "Converted key to Bech32" debug log in toBech32String()
   - Removed "Converted key to hex string" debug log in toHexString()
   - Simplified methods to single return statements

4. Enhanced error logging in BaseKey.toBech32String()
   - Added key type and prefix to error message for better context
   - Improved exception message to include original error

Rationale:
- Low-level data container classes should not log object creation
- These classes are used frequently, logging creates noise
- Constructor logging violates Single Responsibility Principle
- If object creation tracking is needed, use profiler/instrumentation
- Application layer should handle logging when appropriate

Performance impact:
- Reduces log overhead for frequently created objects
- Eliminates unnecessary string formatting on every key creation

Compliance:
- Ch 3: Functions do one thing (no logging side effects)
- Ch 10: Classes have single responsibility (data, not logging)
- Ch 17: Eliminates logging "code smell" in utilities

Ref: LOGGING_REVIEW.md sections 2, 5, and 8

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

nostr-java-base/src/main/java/nostr/base/BaseKey.java

@@ -28,12 +28,10 @@ public abstract class BaseKey implements IKey {
   @Override
   public String toBech32String() {
     try {
-      String bech32 = Bech32.toBech32(prefix, rawData);
-      log.debug("Converted key to Bech32 with prefix {}", prefix);
-      return bech32;
+      return Bech32.toBech32(prefix, rawData);
     } catch (Exception ex) {
-      log.error("Error converting key to Bech32", ex);
-      throw new RuntimeException(ex);
+      log.error("Failed to convert {} key to Bech32 format with prefix {}", type, prefix, ex);
+      throw new RuntimeException("Failed to convert key to Bech32: " + ex.getMessage(), ex);
     }
   }
 
@@ -44,9 +42,7 @@ public String toString() {
   }
 
   public String toHexString() {
-    String hex = NostrUtil.bytesToHex(rawData);
-    log.debug("Converted key to hex string");
-    return hex;
+    return NostrUtil.bytesToHex(rawData);
   }
 
   @Override

nostr-java-base/src/main/java/nostr/base/PrivateKey.java

@@ -13,20 +13,16 @@ public class PrivateKey extends BaseKey {
 
   public PrivateKey(byte[] rawData) {
     super(KeyType.PRIVATE, rawData, Bech32Prefix.NSEC);
-    log.debug("Created private key from byte array");
   }
 
   public PrivateKey(String hexPrivKey) {
     super(KeyType.PRIVATE, NostrUtil.hexToBytes(hexPrivKey), Bech32Prefix.NSEC);
-    log.debug("Created private key from hex string");
   }
 
   /**
    * @return A strong pseudo random private key
    */
   public static PrivateKey generateRandomPrivKey() {
-    PrivateKey key = new PrivateKey(Schnorr.generatePrivateKey());
-    log.debug("Generated new random private key");
-    return key;
+    return new PrivateKey(Schnorr.generatePrivateKey());
   }
 }

nostr-java-base/src/main/java/nostr/base/PublicKey.java

@@ -14,11 +14,9 @@ public class PublicKey extends BaseKey {
 
   public PublicKey(byte[] rawData) {
     super(KeyType.PUBLIC, rawData, Bech32Prefix.NPUB);
-    log.debug("Created public key from byte array");
   }
 
   public PublicKey(String hexPubKey) {
     super(KeyType.PUBLIC, NostrUtil.hexToBytes(hexPubKey), Bech32Prefix.NPUB);
-    log.debug("Created public key from hex string");
   }
 }