v1.0.20

Fix missing diagnostic fields on WiFi-only nodes

Bug: wifi_feeder heartbeat only sent fw_version and uptime_s. On nodes without a BLE adapter (WiFi-only), all diagnostic fields — wifi_ok, cpu_temp_c, wifi_adapter, scanning, mobile, has_gps — arrived as null at the server since those fields only existed in ble_feeder's heartbeat.

Fix: Added get_cpu_temp() and get_wifi_health() to wifi_feeder. Heartbeat now sends the full diagnostic payload from both feeders independently.

Full binary release.