_normalizeJson reads its JSON from stdin (sed | sed | tr) and ignores
any positional argument. dns_czechia_add() called it as
`_normalizeJson "$_res"`, so the response was discarded and the inner
sed blocked reading from stdin.
When issuing for a single domain, or for a record that already exists,
the "already exists" branch returns early and never reaches this call,
which is why the bug stayed hidden. With multiple domains, the first
record often short-circuits on "already exists" while the next,
freshly-added record reaches the broken call and hangs on interactive
runs (or consumes unrelated stdin non-interactively).
Pipe the response into _normalizeJson via stdin, matching
dns_czechia_rm() and every other dnsapi plugin.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
