Enable multi-language font rendering and Unicode text input

Goal:
Allow players to type and display text in any language supported by
Unicode, including Chinese, Japanese, Korean, Thai, Arabic, Korean, Hindi, and more. This
covers all text surfaces: chat editor, chat messages, signs (in-world
and editor), world name/seed, server address/port fields, and all
Iggy Flash UI text fields.

Multi-language support:
Two complementary rendering systems were added to handle Unicode text
across the entire client:

1. Iggy UI (Flash-based text fields): A new UIUnicodeBitmapFont class
   serves Java Minecraft's glyph page PNGs (glyph_00.png-glyph_FF.png)
   through Iggy's bitmap font provider API. Registered as the global
   fallback font with metrics matching the Mojangles bitmap font for
   correct baseline alignment. When the primary bitmap font lacks a
   glyph, it returns IGGY_GLYPH_INVALID and Iggy seamlessly falls back
   to the unicode bitmap font.

2. Legacy C++ Font renderer (chat editor, in-world signs): Revived the
   commented-out unicode glyph page system in Font.cpp. Characters not
   in the bitmap font texture are rendered from glyph page PNGs loaded
   on demand, with proper texture switching mid-string.

3. ChatScreen input: Removed the restrictive acceptableLetters filter
   so all printable Unicode characters are accepted in chat.

Languages now supported for text input and rendering:
- Japanese (Hiragana, Katakana, Kanji)
- Chinese (Simplified and Traditional)
- Korean (Hangul)
- Thai
- Arabic
- Hindi (Devanagari)
- Russian (Cyrillic) - already worked via bitmap font
- Greek - already worked via bitmap font
- Polish, Czech, Turkish (Extended Latin) - already worked via bitmap font
- Armenian, Georgian, and other scripts covered by glyph pages

Security fixes:
- Fixed memset under-initialization of Font::charWidths (zeroed 460
  bytes instead of 460*sizeof(int)=1840 bytes, leaving entries 115+
  uninitialized) - pre-existing bug
- Added bounds checks to all UIUnicodeBitmapFont callbacks to reject
  glyph IDs outside [0, 65535], preventing OOB array access
- Added bounds check in Font::width() section-sign fallback path to
  prevent OOB read on charWidths[] with high codepoints
- Blocked Unicode bidirectional override characters (U+202A-202E,
  U+2066-2069) in chat input to prevent message spoofing

Memory leak fix:
- Fixed SignTileEntity::load allocating wchar_t[256] with new[] on
  every sign load without freeing. Replaced with stack allocation.

Debug logging:
- Added [SIGN] prefixed logging for sign save/update operations
- Added [CHAT] prefixed logging for chat send/receive operations

Files changed:
- UIUnicodeBitmapFont.h/.cpp (new) - Iggy bitmap font for glyph pages
- UIBitmapFont.cpp - Return IGGY_GLYPH_INVALID for unknown chars
- UIFontData.h/.cpp - Added hasGlyph() method
- UIController.h/.cpp - Load and register unicode bitmap fallback font
- UITTFFont.h/.cpp - Added registerAsDefaultFonts parameter
- Font.h/.cpp - Revived unicode glyph page rendering system
- ChatScreen.cpp - Accept all Unicode input, block bidi overrides
- Gui.cpp - Chat display debug logging
- ClientConnection.cpp - Sign update debug logging
- SignTileEntity.cpp - Sign save logging, memory leak fix

Minecraft.Client/Windows64/Windows64_Minecraft.cpp

@@ -506,7 +506,7 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 			break;
 
 		default:
-			return DefWindowProc(hWnd, message, wParam, lParam);
+			return DefWindowProcW(hWnd, message, wParam, lParam);
 		}
 		break;
 	case WM_PAINT:
@@ -563,7 +563,7 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 		else if (vk == VK_MENU)
 			vk = (lParam & (1 << 24)) ? VK_RMENU : VK_LMENU;
 		g_KBMInput.OnKeyDown(vk);
-		return DefWindowProc(hWnd, message, wParam, lParam);
+		return DefWindowProcW(hWnd, message, wParam, lParam);
 	}
 	case WM_KEYUP:
 	case WM_SYSKEYUP:
@@ -661,7 +661,7 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 		}
 		break;
 	default:
-		return DefWindowProc(hWnd, message, wParam, lParam);
+		return DefWindowProcW(hWnd, message, wParam, lParam);
 	}
 	return 0;
 }
@@ -673,23 +673,23 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 //
 ATOM MyRegisterClass(HINSTANCE hInstance)
 {
-	WNDCLASSEX wcex;
+	WNDCLASSEXW wcex;
 
-	wcex.cbSize = sizeof(WNDCLASSEX);
+	wcex.cbSize = sizeof(WNDCLASSEXW);
 
 	wcex.style			= CS_HREDRAW | CS_VREDRAW;
 	wcex.lpfnWndProc	= WndProc;
 	wcex.cbClsExtra		= 0;
 	wcex.cbWndExtra		= 0;
 	wcex.hInstance		= hInstance;
-	wcex.hIcon			= LoadIcon(hInstance, "Minecraft");
+	wcex.hIcon			= LoadIconW(hInstance, L"Minecraft");
 	wcex.hCursor		= LoadCursor(nullptr, IDC_ARROW);
 	wcex.hbrBackground	= (HBRUSH)(COLOR_WINDOW+1);
-	wcex.lpszMenuName	= "Minecraft";
-	wcex.lpszClassName	= "MinecraftClass";
+	wcex.lpszMenuName	= L"Minecraft";
+	wcex.lpszClassName	= L"MinecraftClass";
 	wcex.hIconSm		= LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_MINECRAFTWINDOWS));
 
-	return RegisterClassEx(&wcex);
+	return RegisterClassExW(&wcex);
 }
 
 //
@@ -709,8 +709,8 @@ BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
 	RECT wr = {0, 0, g_rScreenWidth, g_rScreenHeight};    // set the size, but not the position
 	AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);    // adjust the size
 
-	g_hWnd = CreateWindow(	"MinecraftClass",
-		"Minecraft",
+	g_hWnd = CreateWindowW(	L"MinecraftClass",
+		L"Minecraft",
 		WS_OVERLAPPEDWINDOW,
 		CW_USEDEFAULT,
 		0,