Add comprehensive error handling to protocol emulators for production readiness

[Sweekar-cmd]

While reviewing the codebase, I noticed the protocol emulators (coap_pit.c, telnet_pit.c, etc.)
lack robust error handling, which is critical for a production tarpit system.

Current issues identified:

1. No validation of command-line parameters (port, delay, max clients)
2. Missing errno details in error messages
3. No handling of specific error cases (EPIPE, ECONNRESET)
4. No socket options (SO_REUSEADDR, SO_KEEPALIVE)
5. IP address conversion without bounds checking

Proposed changes for coap_pit.c (as a starting point):

• Add parameter validation
• Improve socket creation error messages
• Add sendto()/recvfrom() error checking
• Handle malloc failures gracefully

Why this matters:
Better error handling means:

• Easier debugging when things go wrong
• More reliable tarpit operation
• Better metrics for the Grafana dashboard

I'd like to work on this if the maintainers agree it's valuable.