feat(cli): add --json output to paired-devices add/remove

[neto7z]

Closes #221

Extends the existing --json support to the last two paired-devices commands that still printed plain text:

• paired-devices add --json now outputs the paired device as an object with the same shape as paired-devices list --json (macAddress / model / isDemo, camelCase).
• paired-devices remove --json now outputs the removed mac address: {"macAddress": "00:00:00:00:00:02"}.

Human-readable output (Paired / Unpaired) is unchanged, and --json was not previously accepted by these two commands.

Tested headless with demo devices (--demo) against a throwaway database. cargo clippy -p openscq30-cli -- -D warnings and cargo fmt --all -- --check both pass.

Example:

$ openscq30 paired-devices add --json -a 00:00:00:00:00:02 -m SoundcoreA3028 --demo
{
  "macAddress": "00:00:00:00:00:02",
  "model": "SoundcoreA3028",
  "isDemo": true
}

$ openscq30 paired-devices remove --json -a 00:00:00:00:00:02
{
  "macAddress": "00:00:00:00:00:02"
}

[Oppzippy]

Sorry for the delay reviewing.

Is this useful? It's only outputting information that was passed in via CLI arguments, so the caller has all of this information already.