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/websocket.h

@@ -0,0 +1,47 @@
+#ifndef WEBSOCKET_H
+#define WEBSOCKET_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <openssl/ssl.h>
+
+// WebSocket opcodes
+#define WS_OPCODE_CONTINUATION 0x0
+#define WS_OPCODE_TEXT         0x1
+#define WS_OPCODE_BINARY       0x2
+#define WS_OPCODE_CLOSE        0x8
+#define WS_OPCODE_PING         0x9
+#define WS_OPCODE_PONG         0xA
+
+// WebSocket frame header structure
+typedef struct {
+    uint8_t fin;
+    uint8_t opcode;
+    uint8_t mask;
+    uint64_t payload_length;
+    uint8_t masking_key[4];
+} ws_frame_header_t;
+
+// WebSocket connection context
+typedef struct {
+    int socket_fd;
+    SSL *ssl;
+    bool is_ssl;
+    bool handshake_complete;
+} ws_connection_t;
+
+// Function prototypes
+int ws_handle_handshake(int client_socket, const char *request, char *response, size_t response_size);
+int ws_handle_handshake_ssl(SSL *ssl, const char *request, char *response, size_t response_size);
+int ws_parse_frame(const uint8_t *data, size_t len, ws_frame_header_t *header, uint8_t **payload);
+int ws_create_frame(uint8_t *buffer, size_t buffer_size, uint8_t opcode, const uint8_t *payload, size_t payload_len);
+int ws_send_frame(ws_connection_t *conn, uint8_t opcode, const uint8_t *payload, size_t payload_len);
+int ws_send_text(ws_connection_t *conn, const char *text);
+int ws_send_pong(ws_connection_t *conn, const uint8_t *payload, size_t payload_len);
+void ws_close_connection(ws_connection_t *conn, uint16_t status_code);
+
+// Helper functions
+char* ws_generate_accept_key(const char *client_key);
+bool ws_is_valid_utf8(const uint8_t *data, size_t len);
+
+#endif