fix(zk_toolbox): fix port offset for new chains

[sanekmelnikov]

What ❔

Fixed port offset for newly created chains via zk_inception:

• Use chain.id instead of chain.chain_id
• Use (chain.id - 1) * 100 as an offset to keep the port for the first chain as 3050

Why ❔

Using chain.chain_id was not intended as the resulting port number could potentially overflow.

Checklist

• PR title corresponds to the body of PR (we generate changelog entries from PRs).
• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.
• Code has been formatted via zk fmt and zk lint.

[manuelmauro]

LGTM