Check up to 1,000 at once

POST a JSON body with up to 1,000 proxies. They are checked in parallel and the answer comes back in one response within about 25 seconds: a few seconds when they are alive, longer when some never answer. The response is { "count": n, "results": [ ... ], "complete": true, "unchecked": 0 } with the same per-proxy shape, one row for every line you sent. A line that did not get an answer inside the time budget comes back with status: "unchecked", and complete is then false: retry those lines, or stream the list instead. Bigger lists belong on the streaming endpoint below, which takes up to 100,000 and reports each proxy the moment it settles.