Enhance Healthchecks with up/down livestats

[steven-s-martins]

Summary

Add enhanced support to the existing Healthchecks app so the tile shows Up / Down check counts, similar to Uptime Kuma and Kuvasz Uptime. Implementation follows the Kuvasz Uptime pattern closely (JSON list endpoint, API-key header, Up/Down livestats, dataonly refresh).

• Stats (tile): Up / Down (counts by check status)
• Endpoint: GET /api/v3/checks/ for both Test and livestats
• Auth: API key via X-Api-Key header (read-only keys work)
• Cadence: dataonly=1 — up/down counts refresh on the 30s interval
• Statuses counted: up and down only (new / grace / paused are ignored)

Test plan

Tested against my self-hosted Healthchecks and Heimdall instances:

• Config Test succeeds with a valid API key and fails with a bad/missing key
• Tile Up/Down counts match GET /api/v3/checks/
• Read-only API key works for listing checks

[KodeStar]

Reviewed and merging — thanks for this, the Kuvasz pattern was the right one to follow here.

I pushed one fix onto the branch before merge. execute() is configured with http_errors => false, so a 401 from a missing/revoked API key comes back as a real response whose body is {"error": "wrong api key"} — a stdClass with no checks property. is_object($body) ? $body->checks : [] read that property directly, which raises an undefined-property warning; Laravel promotes that to an ErrorException, so get_stats returned a 500 and the tile errored out instead of falling back to zeroed counts.

The fix coalesces to null ($body->checks ?? null) so a malformed or error response leaves the tile alone, and moves the active status onto the success path — KuvaszUptime flips to active when the list parses, and the original always returned inactive. With dataonly=1 that only affects the refresh cadence, but it keeps the two apps consistent.