Implement HTTP/2 and WebSocket support; remove legacy JavaScript and CSS files

- Added HTTP/2 support in src/http2.c and src/http2.h, including session management, frame handling, and response sending.
- Introduced WebSocket functionality in src/websocket.c and src/websocket.h, covering handshake, frame parsing, and message sending.
- Created a WebSocket test page (www/websocket-test.html) for client-side interaction.
- Removed outdated JavaScript (www/script.js) and CSS (www/style.css) files.

src/http2.h

@@ -0,0 +1,41 @@
+#ifndef HTTP2_H
+#define HTTP2_H
+
+#include <nghttp2/nghttp2.h>
+#include <openssl/ssl.h>
+#include <stdbool.h>
+
+// HTTP/2 session context
+typedef struct {
+    nghttp2_session *session;
+    SSL *ssl;
+    int client_socket;
+    bool handshake_complete;
+} http2_session_t;
+
+// HTTP/2 stream data
+typedef struct {
+    int32_t stream_id;
+    char request_path[256];
+    char *request_method;
+    int fd;  // File descriptor for response
+    size_t file_size;
+    char *mime_type;
+    char *content_length;
+} http2_stream_data_t;
+
+// Function prototypes
+int http2_session_init(http2_session_t *session, int client_socket, SSL *ssl);
+void http2_session_cleanup(http2_session_t *session);
+int http2_handle_connection(http2_session_t *session);
+int http2_send_response(http2_session_t *session, int32_t stream_id, 
+                        const char *data, size_t len, bool end_stream);
+int http2_send_error(http2_session_t *session, int32_t stream_id, 
+                     int status_code, const char *message);
+
+// ALPN callback for protocol selection
+int alpn_select_proto_cb(SSL *ssl, const unsigned char **out,
+                        unsigned char *outlen, const unsigned char *in,
+                        unsigned int inlen, void *arg);
+
+#endif