Do not log pairing secrets in ExchangeHandler

Remove DEBUG log statements that printed the SRP shared secret K, the
HKDF-derived encryption key and the raw M5 auth tag / message data.
No logic changes.

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

Author: udaw

CHANGES.md

@@ -1,5 +1,6 @@
 # HAP-Java 2.0.9
 * Fix Set Duration and Remaining Duration characteristics to advertise format `uint32` instead of `int` [#202](https://github.com/hap-java/HAP-Java/issues/202)
+* Stop logging the SRP shared secret, derived key and M5 message data during pairing at DEBUG level
 
 # HAP-Java 2.0.8
 * Updated bouncy castle to 1.83

src/main/java/io/github/hapjava/server/impl/pairing/ExchangeHandler.java

@@ -31,8 +31,6 @@ public ExchangeHandler(byte[] k, HomekitAuthInfo authInfo) {
   }
 
   public HttpResponse handle(PairSetupRequest req) throws Exception {
-    LOGGER.debug("ExchangeHandler: Starting M5 exchange with shared secret K: {}", bytesToHex(k));
-
     HKDFBytesGenerator hkdf = new HKDFBytesGenerator(new SHA512Digest());
     hkdf.init(
         new HKDFParameters(
@@ -42,15 +40,10 @@ public HttpResponse handle(PairSetupRequest req) throws Exception {
     byte[] okm = hkdf_enc_key = new byte[32];
     hkdf.generateBytes(okm, 0, 32);
 
-    LOGGER.debug("ExchangeHandler: HKDF encryption key: {}", bytesToHex(okm));
-
     return decrypt((ExchangeRequest) req, okm);
   }
 
   private HttpResponse decrypt(ExchangeRequest req, byte[] key) throws Exception {
-    LOGGER.debug("ExchangeHandler: Received AuthTag: {}", bytesToHex(req.getAuthTagData()));
-    LOGGER.debug("ExchangeHandler: Received MessageData: {}", bytesToHex(req.getMessageData()));
-
     try {
       ChachaDecoder chacha = new ChachaDecoder(key, "PS-Msg05".getBytes(StandardCharsets.UTF_8));
       byte[] plaintext = chacha.decodeCiphertext(req.getAuthTagData(), req.getMessageData());