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.

Minecraft.Client/Common/UI/UIScene_HUD.h

@@ -25,6 +25,7 @@ protected:
 	IggyName m_funcRepositionHud, m_funcSetDisplayName, m_funcSetTooltipsEnabled;
 	IggyName m_funcSetRidingHorse, m_funcSetHorseHealth, m_funcSetHorseJumpBarProgress;
 	IggyName m_funcSetHealthAbsorb;
+	IggyName m_funcSetHardcore;
 	UI_BEGIN_MAP_ELEMENTS_AND_NAMES(UIScene)
 		UI_MAP_ELEMENT(m_labelChatText[0],"Label1")
 		UI_MAP_ELEMENT(m_labelChatText[1],"Label2")
@@ -89,6 +90,7 @@ protected:
 		UI_MAP_NAME(m_funcSetHorseJumpBarProgress, L"SetHorseJumpBarProgress")
 		
 		UI_MAP_NAME(m_funcSetHealthAbsorb, L"SetHealthAbsorb")
+		UI_MAP_NAME(m_funcSetHardcore, L"SetHardcore")
 	UI_END_MAP_ELEMENTS_AND_NAMES()
 
 public:
@@ -159,6 +161,8 @@ private:
 
 	void SetHealthAbsorb(int healthAbsorb);
 
+	void SetHardcoreMode(bool bHardcore);
+
 public:
 	void SetSelectedLabel(const wstring &label);
 	void ShowDisplayName(bool show);