refactor: drop Joda-Time (-> java.time) and make protocol charsets explicit

Modernization following the dependency upgrades:
- Joda-Time was used in exactly one place (ModToolSanctionInfoComposer, to
  subtract probation days from a Date). Migrated to java.time
  (Instant/ZoneId.systemDefault, calendar-accurate like the old Joda call) and
  removed the joda-time dependency entirely — confirmed gone from the shaded jar.
- Make string<->bytes conversions explicitly UTF-8 instead of relying on the
  platform default. Most importantly the wire codec (ClientMessage.readString /
  ServerMessage.appendString) — both sides now pinned to UTF-8 so international
  characters are robust regardless of -Dfile.encoding. Also RCONServerHandler,
  PluginManager and the WS origin-forbidden response.

Verified: clean compile, 15/15 tests, shaded jar.

Emulator/pom.xml

@@ -163,13 +163,6 @@
             <version>2.4.3</version>
         </dependency>
 
-        <!-- Joda Time -->
-        <dependency>
-            <groupId>joda-time</groupId>
-            <artifactId>joda-time</artifactId>
-            <version>2.14.2</version>
-        </dependency>
-
         <!-- jBCrypt � used by the built-in /api/auth/* HTTP login handler
              to verify Laravel-style $2y$ BCrypt hashes from users.password -->
         <dependency>

Emulator/src/main/java/com/eu/habbo/messages/ClientMessage.java

@@ -4,6 +4,8 @@ import com.eu.habbo.util.PacketUtils;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 
+import java.nio.charset.StandardCharsets;
+
 public class ClientMessage {
     private final int header;
     private final ByteBuf buffer;
@@ -71,7 +73,7 @@ public class ClientMessage {
             }
             byte[] data = new byte[length];
             this.buffer.readBytes(data);
-            return new String(data);
+            return new String(data, StandardCharsets.UTF_8);
         } catch (Exception e) {
             return "";
         }

Emulator/src/main/java/com/eu/habbo/messages/ServerMessage.java

@@ -7,6 +7,7 @@ import io.netty.buffer.ByteBufOutputStream;
 import io.netty.buffer.Unpooled;
 
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 
 public class ServerMessage {
 
@@ -61,7 +62,7 @@ public class ServerMessage {
         }
 
         try {
-            byte[] data = obj.getBytes();
+            byte[] data = obj.getBytes(StandardCharsets.UTF_8);
             this.stream.writeShort(data.length);
             this.stream.write(data);
         } catch (IOException e) {

Emulator/src/main/java/com/eu/habbo/messages/outgoing/modtool/ModToolSanctionInfoComposer.java

@@ -9,8 +9,8 @@ import com.eu.habbo.messages.ServerMessage;
 import com.eu.habbo.messages.outgoing.MessageComposer;
 import com.eu.habbo.messages.outgoing.Outgoing;
 import gnu.trove.map.hash.THashMap;
-import org.joda.time.DateTime;
 
+import java.time.ZoneId;
 import java.util.ArrayList;
 import java.util.Date;
 
@@ -47,7 +47,10 @@ public class ModToolSanctionInfoComposer extends MessageComposer {
                 if (item.probationTimestamp > 0) {
                     probationEndTime = new Date((long) item.probationTimestamp * 1000);
 
-                    probationStartTime = new DateTime(probationEndTime).minusDays(modToolSanctions.getProbationDays(modToolSanctionLevelItem)).toDate();
+                    probationStartTime = Date.from(probationEndTime.toInstant()
+                            .atZone(ZoneId.systemDefault())
+                            .minusDays(modToolSanctions.getProbationDays(modToolSanctionLevelItem))
+                            .toInstant());
 
                     Date tradeLockedUntil = null;
 

Emulator/src/main/java/com/eu/habbo/networking/gameserver/handlers/WebSocketHttpHandler.java

@@ -54,7 +54,7 @@ public class WebSocketHttpHandler extends ChannelInboundHandlerAdapter {
             FullHttpResponse response = new DefaultFullHttpResponse(
                     HttpVersion.HTTP_1_1,
                     HttpResponseStatus.FORBIDDEN,
-                    Unpooled.wrappedBuffer("Origin forbidden".getBytes())
+                    Unpooled.wrappedBuffer("Origin forbidden".getBytes(java.nio.charset.StandardCharsets.UTF_8))
             );
             response.headers().set("Vary", "Origin");
             ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);

Emulator/src/main/java/com/eu/habbo/networking/rconserver/RCONServerHandler.java

@@ -41,7 +41,7 @@ public class RCONServerHandler extends ChannelInboundHandlerAdapter {
 
         byte[] d = new byte[data.readableBytes()];
         data.getBytes(0, d);
-        String message = new String(d);
+        String message = new String(d, java.nio.charset.StandardCharsets.UTF_8);
         Gson gson = GSON;
         String response = "ERROR";
         String key = "";
@@ -56,7 +56,7 @@ public class RCONServerHandler extends ChannelInboundHandlerAdapter {
             e.printStackTrace();
         }
 
-        ChannelFuture f = ctx.channel().write(Unpooled.copiedBuffer(response.getBytes()), ctx.channel().voidPromise());
+        ChannelFuture f = ctx.channel().write(Unpooled.copiedBuffer(response.getBytes(java.nio.charset.StandardCharsets.UTF_8)), ctx.channel().voidPromise());
         ctx.channel().flush();
         ctx.flush();
         f.channel().close();

Emulator/src/main/java/com/eu/habbo/plugin/PluginManager.java

@@ -277,7 +277,7 @@ public class PluginManager {
                 byte[] content = new byte[stream.available()];
 
                 if (stream.read(content) > 0) {
-                    String body = new String(content);
+                    String body = new String(content, java.nio.charset.StandardCharsets.UTF_8);
 
                     HabboPluginConfiguration pluginConfigurtion = PLUGIN_GSON.fromJson(body, HabboPluginConfiguration.class);