Fix Content-Length based request parsing

[greatm3]

Description:

Current implementation uses data.includes("\r\n\r\n") to detect request end. This is vulnerable to request smuggling if the body contains \r\n\r\n. Need to parse Content-Length header and only consider request complete when exact number of bytes received.

Tasks:

• Parse Content-Length header from request headers
• Calculate total expected bytes: headerEndIndex + 4 + contentLength
• Only trigger request handler when data.length >= expectedBytes
• Handle GET/HEAD requests with no body (Content-Length: 0 or missing)
• Add validation for invalid Content-Length values

Files to modify:

• src/httpServer.ts - data event handler
• src/utils/utils.ts - parseRequestMessage function

References:

• RFC 7230 Section 3.3.3 (Message Body Length)
• CWE-444: HTTP Request Smuggling