feat: implement hardcore hearts with game mode lock

Display hardcore heart textures when a world is in hardcore mode,
matching Java Edition behavior. Hearts switch between normal/hardcore
across all states (poison, wither, flash) and all HUD resolutions.

C++ changes:
- IUIScene_HUD: check isHardcore() and call SetHardcoreMode() each tick
- UIScene_HUD: send hardcore boolean to Flash via Iggy, invalidate
  SetHealth dirty check on state change to force heart redraw
- CreateWorldMenu/LoadMenu: lock game mode to Survival when hardcore
- MinecraftServer: gate server.properties hardcore override behind
  MINECRAFT_SERVER_BUILD so offline worlds preserve their saved flag

SWF changes (via new Java tools):
- AddHardcoreBitmaps: adds 10 hardcore heart bitmaps to graphics SWFs
- AddHardcoreHearts: adds 10 new frames (15-24) to health sprite
- PatchHudABC: patches HUD ActionScript bytecode with SetHardcore
  method and frame offset logic (+14 normal/poison, +6 wither)

Also updates README changelog styling with consistent ### headings.

tools/DecompileASBody.java

@@ -0,0 +1,48 @@
+import com.jpexs.decompiler.flash.SWF;
+import com.jpexs.decompiler.flash.exporters.modes.ScriptExportMode;
+import com.jpexs.decompiler.flash.exporters.settings.ScriptExportSettings;
+import com.jpexs.decompiler.flash.configuration.Configuration;
+import java.io.*;
+import java.util.*;
+
+/**
+ * Exports all ActionScript 3 source from a SWF to a directory.
+ * Usage: DecompileASBody <swf-file> [output-dir]
+ */
+public class DecompileASBody {
+    public static void main(String[] args) throws Exception {
+        if (args.length < 1) {
+            System.out.println("Usage: DecompileASBody <swf-file> [output-dir]");
+            return;
+        }
+
+        Configuration.autoDeobfuscate.set(false);
+
+        String path = args[0];
+        String outDir = args.length > 1 ? args[1] : "as_output";
+
+        SWF swf = new SWF(new FileInputStream(path), false);
+
+        File out = new File(outDir);
+        out.mkdirs();
+
+        ScriptExportSettings settings = new ScriptExportSettings(ScriptExportMode.AS, false, false, false, false);
+        swf.exportActionScript(null, outDir, settings, false, null);
+
+        System.out.println("Export complete. Files:");
+        listFiles(new File(outDir), "");
+    }
+
+    static void listFiles(File dir, String prefix) {
+        File[] files = dir.listFiles();
+        if (files == null) return;
+        Arrays.sort(files);
+        for (File f : files) {
+            if (f.isDirectory()) {
+                listFiles(f, prefix + f.getName() + "/");
+            } else {
+                System.out.println("  " + prefix + f.getName() + " (" + f.length() + " bytes)");
+            }
+        }
+    }
+}