fix(dex): reject same-token (base==quote) pools on create and remove

addInternal used Java reference equality (!=) on freshly-deserialized
score.Address params, so the base!=quote guard was a silent no-op and
base==quote pools could be created. Switch to value equality (.equals).
Add the same guard to _remove so any pre-existing same-token pool cannot
be drained via the DictDB key-collision double-credit. Bump DEX to v1.1.9.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: AntonsAssistant

core-contracts/Dex/src/main/java/network/balanced/score/core/dex/DexImpl.java

@@ -289,6 +289,7 @@ void _remove(BigInteger _id, NetworkAddress _user, BigInteger _value, @Optional
         require(_value.compareTo(userBalance) <= 0, TAG + ": Insufficient balance");
 
         Address quoteToken = poolQuote.get(_id.intValue());
+        require(!baseToken.equals(quoteToken), TAG + ": Invalid same-token pool, removal blocked");
         DictDB<Address, BigInteger> totalTokensInPool = poolTotal.at(_id.intValue());
         BigInteger totalBase = totalTokensInPool.get(baseToken);
         BigInteger totalQuote = totalTokensInPool.get(quoteToken);
@@ -350,7 +351,7 @@ public void addInternal(NetworkAddress _from, Address _baseToken, Address _quote
         // If none is found (return 0), we create a new pool.
         Integer id = poolId.at(_baseToken).getOrDefault(_quoteToken, 0);
 
-        require(_baseToken != _quoteToken, TAG + ": Pool must contain two token contracts");
+        require(!_baseToken.equals(_quoteToken), TAG + ": Pool must contain two token contracts");
         // Check base/quote balances are valid
         require(_baseValue.compareTo(BigInteger.ZERO) > 0,
                 TAG + ": Cannot send 0 or negative base token");

score-lib/src/main/java/network/balanced/score/lib/utils/Versions.java

@@ -30,7 +30,7 @@ public class Versions {
     public final static String STABILITY = "v1.1.1";
     public final static String BALANCEDORACLE = "v1.2.0";
     public final static String DAOFUND = "v1.1.4";
-    public final static String DEX = "v1.1.8";
+    public final static String DEX = "v1.1.9";
     public final static String GOVERNANCE = "v1.0.2";
     public final static String REBALANCING = "v1.0.0";
     public final static String ROUTER = "v1.2.4";