- Remove monotonic counter writes to NVS (stop burning flash on every
event). Derive head and cnt by scanning slots on boot.
- Widen seq to uint32 so slot scan works across multi-year lifetimes.
- Add FreeRTOS mutex around write/read so WiFi event handlers can
safely call event_log_write from another task.
- Check Preferences.begin() return; disable logging if NVS unavailable.
- Extract NTP_SYNC_THRESHOLD constant; drop misleading native uptime.
- Add tests for empty read, max_entries truncation, real-path hash.
Peter Woolery
95f91d3656