Fix argparse crash on Python 3.14

[suhlig]

The reconnect, reboot, wps, devices and calls subcommands were registered as positional arguments with action="store_true". Python 3.14's argparse now rejects actions with nargs == 0 on positional arguments, so the CLI raised ValueError: action 'store_true' is not valid for positional arguments at startup for every invocation.

These positionals only existed to capture which subcommand was selected, since the subparsers had no dest. This change captures the command via add_subparsers(dest="command") and drops the bogus positionals, which is the idiomatic argparse approach.

Verified argument parsing and --help output on Python 3.12, 3.13 and 3.14.

[Wkhanex]

Additional dispatch regression check on this head: the five no-argument commands and both on/off variants of wifi, guest-wifi and office-wifi parsed correctly (11 combinations), with command identifying the selected subparser and the Wi-Fi values preserved. Extracted check_args also awaited exactly the intended mocked route for wps, reconnect and reboot. This supports replacing the positional store_true flags with the subparser destination. Consider keeping these parser/AsyncMock checks as tests so a future command rename cannot disconnect parsing from dispatch. I ran these checks on Python 3.12; no real router was contacted and Python 3.14/full package tests were not run.