Add man page (logreaper.1)

[bad-antics]

Description

LogReaper should ship with a proper Unix man page so users can run man logreaper after install.

Details

• Create doc/logreaper.1 in roff/troff format
• Update Makefile install target to copy it to $(PREFIX)/share/man/man1/
• Cover all CLI flags (-v, -j, -c, -f, -o, etc.)
• Include examples section
• Reference: https://man7.org/linux/man-pages/man7/man-pages.7.html

Acceptance Criteria

• Man page renders correctly with man ./doc/logreaper.1
• make install installs the man page
• All current CLI options are documented