Add GPU error handling and performance optimizations

Introduces a comprehensive GPU configuration and fallback system to resolve GPU process launch failures (Error 18), including new modules for GPU management and performance monitoring. Adds a GPU diagnostics HTML page, optimized CSS for rendering, and a diagnostic startup script. Updates main and preload scripts for improved stability, async file operations, and enhanced API exposure. Site history and bookmarks handling are optimized for performance and reliability.

start-gpu-safe.bat

@@ -0,0 +1,48 @@
+@echo off
+echo Starting Nebula Browser with GPU diagnostics...
+echo.
+
+REM Check if running with administrator privileges
+net session >nul 2>&1
+if %errorLevel% neq 0 (
+    echo Warning: Not running as administrator. Some GPU features may not work.
+    echo Consider running as administrator if you encounter GPU issues.
+    echo.
+)
+
+REM Set environment variables for better GPU support
+set ELECTRON_ENABLE_LOGGING=1
+set ELECTRON_LOG_FILE=gpu-debug.log
+
+REM Alternative GPU configurations
+echo Choose GPU configuration:
+echo 1. Default (recommended)
+echo 2. Force GPU acceleration
+echo 3. Disable GPU (software rendering)
+echo 4. Debug mode with verbose logging
+echo.
+set /p choice="Enter choice (1-4): "
+
+if "%choice%"=="1" (
+    echo Starting with default GPU configuration...
+    npm start
+) else if "%choice%"=="2" (
+    echo Forcing GPU acceleration...
+    set ELECTRON_FORCE_HARDWARE_ACCELERATION=1
+    npm start
+) else if "%choice%"=="3" (
+    echo Using software rendering...
+    set ELECTRON_DISABLE_GPU=1
+    npm start -- --disable-gpu
+) else if "%choice%"=="4" (
+    echo Starting in debug mode...
+    set ELECTRON_ENABLE_STACK_DUMPING=1
+    npm start -- --enable-logging --log-level=0 --vmodule=gpu*=3
+) else (
+    echo Invalid choice, using default...
+    npm start
+)
+
+echo.
+echo Browser closed. Check gpu-debug.log for GPU-related messages.
+pause