Downloads balance-firmware.bin from Gitea release URL to inactive OTA
partition, streams SHA256 verification via mbedTLS, sets boot partition
and reboots. Auto-rollback via CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE if
ota_self_health_check() not called within 30 s of boot. Progress 0-100%
in g_ota_self_progress for display task.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
