Enhance server configuration and performance optimizations

- Added max_connections option to server configuration
- Updated Makefile to include performance.c and related headers
- Implemented memory-mapped file caching and buffer pooling for improved performance
- Refactored config parser to handle new configuration options
- Increased maximum request size and optimized file handling

src/server_config.h

@@ -15,6 +15,7 @@ typedef struct {
     bool enable_http2;
     bool enable_websocket;
     char www_path[256];
+    int max_connections;
 } ServerConfig;
 
 int load_config(const char *filename, ServerConfig *config);