Add embedded assets, splash screens, and asset loading support

Features added:
- Embedded main.lua and Lua files support (EMBED_MAIN option)
- Embedded assets support (EMBED_ASSETS option)
- Splash screens with dual logo display (always embedded)
- Asset loading progress tracking API (BeginAssetLoading, UpdateAssetLoading, EndAssetLoading)
- Custom font embedding for splash/loading screens
- --log flag for Windows console control
- --no-logo flag to skip splash screens in development
- Python scripts for embedding (embed_lua.py, embed_assets.py, embed_logo.py, embed_font.py)
- Documentation (EMBEDDING.md, ASSET_LOADING.md, SPLASH_SCREENS.md)

This allows building single-executable releases with all Lua code and assets embedded.

embed_font.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+"""
+Embed font file into C header.
+Usage: python embed_font.py <output.h> <font.ttf>
+"""
+
+import sys
+import os
+
+def embed_file(file_path, var_name):
+    """Convert a file to a C byte array"""
+    with open(file_path, 'rb') as f:
+        data = f.read()
+    
+    output = f"/* {os.path.basename(file_path)} */\n"
+    output += f"static const unsigned char {var_name}[] = {{\n"
+    
+    # Write bytes in rows of 16
+    for i in range(0, len(data), 16):
+        chunk = data[i:i+16]
+        hex_values = ', '.join(f'0x{b:02x}' for b in chunk)
+        output += f"    {hex_values},\n"
+    
+    output += "};\n"
+    output += f"static const unsigned int {var_name}_size = {len(data)};\n\n"
+    
+    return output
+
+def main():
+    if len(sys.argv) != 3:
+        print("Usage: python embed_font.py <output.h> <font.ttf>")
+        sys.exit(1)
+    
+    output_file = sys.argv[1]
+    font_file = sys.argv[2]
+    
+    # Check if file exists
+    if not os.path.exists(font_file):
+        print(f"Error: {font_file} not found!")
+        sys.exit(1)
+    
+    # Generate header content
+    header_content = "/* Auto-generated embedded font file */\n"
+    header_content += "#pragma once\n\n"
+    
+    # Embed font file
+    header_content += embed_file(font_file, "embedded_font_data")
+    
+    # Write to output file
+    with open(output_file, 'w') as f:
+        f.write(header_content)
+    
+    print(f"Generated {output_file}")
+    print(f"  - Embedded {font_file} ({os.path.getsize(font_file)} bytes)")
+
+if __name__ == "__main__":
+    main()