feat: add port search, remote sort, export, and process info

[karol-broda]

fixes #20 #21 #22 #23

• search now matches against port numbers and pid (so /3000 finds connections on port 3000)
• sort cycle includes remote address and remote port options
• export modal in tui lets you pick csv or tsv format and shows a preview of what will be exported
• added -O/--output-file flag to snitch ls for cli export
• connections include cmdline and cwd fields, visible in detail view and json output

tested on linux, includes unit tests for all changes.