Fix auto-ping timer firing 8s early due to setInterval/countdown desync

[Copilot]

Auto-ping countdown showed ~8s remaining when the ping fired because setInterval started at T=0 but countdown display only started after the ~7s API delay completed.

Changes

Replaced interval-based timing with sequential scheduling:

• setInterval → setTimeout chain where each ping schedules the next after completion
• New scheduleNextAutoPing() atomically starts countdown and schedules next ping
• sendPing() calls scheduleNextAutoPing() after API POST + map refresh complete
• startAutoPing() simplified to only trigger first ping

Timing flow:

// Before: setInterval from T=0, countdown from T=7 → 8s desync
startAutoPing() → setInterval(15s) | sendPing() → [7s delay] → countdown starts

// After: setTimeout from completion time → perfect sync  
startAutoPing() → sendPing() → [7s delay] → scheduleNextAutoPing() → countdown + setTimeout(15s)

Cleanup:

• clearInterval → clearTimeout in stopAutoPing()
• Existing state.running guard prevents race conditions

Original prompt

Since the last merge things seem to be working better, heres a new issue we need fixed.

When Start Auto Ping is enabled with a 15-second interval (the same issue occurs at 30 seconds), the countdown initially behaves correctly (15, 14, 13, 12, etc.). However, at approximately 8 seconds remaining, the status briefly switches to “ping sent / waiting for API” and then immediately returns to the countdown.

Expected auto-ping behavior:

A ping must be sent only when the countdown reaches 0.

After the ping is sent, the app should stay in “waiting for API” until the API POST completes.

Once the API response is received and the iframe has refreshed, a new full interval countdown (for example, 15 seconds) should begin.

Current behavior indicates the auto-ping send logic is firing early, rather than being strictly tied to the countdown reaching zero.

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