Adds gitea_ota_check_task on Balance board: fetches Gitea releases API
every 30 min and on boot, filters by esp32-balance/ and esp32-io/ tag
prefixes, compares semver against embedded FW version, stores update info
(version string, download URL, SHA256) in g_balance_update / g_io_update.
WiFi credentials read from NVS namespace "wifi"; falls back to compile-time
DEFAULT_WIFI_SSID/PASS if NVS is empty.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
