introduced AntiIllegalSignCharacters appliance to prevent usage of illegal characters in sign edits

common/src/main/java/eu/mhsl/craftattack/spawn/common/appliances/security/antiIllegalSignCharacters/AntiIllegalSignCharacters.java

@@ -0,0 +1,16 @@
+package eu.mhsl.craftattack.spawn.common.appliances.security.antiIllegalSignCharacters;
+
+import eu.mhsl.craftattack.spawn.core.appliance.Appliance;
+import org.bukkit.event.Listener;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+
+public class AntiIllegalSignCharacters extends Appliance {
+    @Override
+    protected @NotNull List<Listener> listeners() {
+        return List.of(
+            new SignEditListener()
+        );
+    }
+}

common/src/main/java/eu/mhsl/craftattack/spawn/common/appliances/security/antiIllegalSignCharacters/SignEditListener.java

@@ -0,0 +1,23 @@
+package eu.mhsl.craftattack.spawn.common.appliances.security.antiIllegalSignCharacters;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.serializer.plain.PlainTextComponentSerializer;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.block.SignChangeEvent;
+
+class SignEditListener extends ApplianceListener<AntiIllegalSignCharacters> {
+    @EventHandler
+    public void onSignEdit(SignChangeEvent event) {
+        for (int i = 0; i < 4; i++) {
+            Component line = event.line(i);
+            if(line == null) continue;
+            String lineStr = PlainTextComponentSerializer.plainText().serialize(line);
+
+            if (!lineStr.matches("^[ -~]*$")) {
+                String cleaned = lineStr.replaceAll("[^ -~]", "");
+                event.line(i, Component.text(cleaned));
+            }
+        }
+    }
+}