Wi-Fi credentials now live in the widget's own NVS (up to 8 networks)
instead of the driver's single slot. The save handler just appends to
the list and reboots, so it no longer calls esp_wifi_set_config in
APSTA mode -- the source of the intermittent could-not-save. A connect
task cycles the saved networks newest-first and holds the first that
connects, re-scanning on drop, so the widget follows you between
locations. The portal lists saved networks with a Forget button and an
add form. An existing driver-stored credential is migrated on first
boot. Verified end to end over the LAN: save persists across reboot,
forget removes.