Man pages (netleak(8))

[MuriloChianfa]

Write comprehensive manual pages for the netleak CLI and the netleakd daemon to improve user documentation and discoverability.

Tasks:

• Write netleak(8) man page covering command-line arguments, interface selection, and examples.
• Write netleakd(8) man page covering daemon configuration, signals, and systemd integration.
• Add a make install-man target to the Makefile to deploy the man pages to /usr/share/man/man8/.
• Ensure packaging workflows (DEB/RPM) include the new man pages.