fix(netmgr): mirror sta_configured in memory when credentials change

s_net.sta_configured was computed once at boot from NVS, then never
updated when netmgr_set_credentials() persisted new creds. The result:
on first-time onboarding (fresh-NVS device), the in-memory flag stayed
false even after the user saved creds + STA successfully connected.

ap_should_be_on() checks sta_configured first and unconditionally
returns true if false — which meant the IP_EVENT_STA_GOT_IP handler
saw "AP should still be on" even after STA was up, never armed the
AP teardown timer, and the AP stayed broadcasting forever.

Symptom (from bench): user onboards via captive portal, success modal
shows the IP, device is reachable on home Wi-Fi, but AmbiSense-XXXX
remains visible in the phone's Wi-Fi list indefinitely.

Reboots after the first onboarding worked correctly because the
init path re-reads NVS and computes sta_configured = true.

Fix: set s_net.sta_configured = true alongside settings_set_wifi_ssid()
in the success path, and = false alongside the clear path.

Reproduced on a freshly-erased ESP32-C3 (MAC d8:3b:da:35:06:f0)
running v6.1.0-alpha.2; verified fixed on the same hardware.

Author: Ravi Singh

firmware/components/netmgr/netmgr.c

@@ -476,13 +476,23 @@ esp_err_t netmgr_set_credentials(const char *ssid, const char *pass) {
     if (!ssid || !ssid[0]) {
         settings_set_wifi_ssid("");
         settings_set_wifi_pass("");
+        /* CRITICAL: clear in-memory flag too, otherwise ap_should_be_on()
+         * still thinks we're configured and keeps the AP up incorrectly. */
+        s_net.sta_configured = false;
         esp_wifi_disconnect();
         notify_state(NETMGR_STATE_AP_FALLBACK);
         ESP_LOGI(TAG, "Cleared STA creds; AP remains up");
         return ESP_OK;
     }
     settings_set_wifi_ssid(ssid);
     settings_set_wifi_pass(pass ? pass : "");
+    /* CRITICAL: mark STA configured BEFORE the connection attempt. The
+     * IP_EVENT_STA_GOT_IP handler reads ap_should_be_on() which depends
+     * on this flag — without setting it here, fresh-NVS onboarding
+     * leaves the AP up forever even after STA succeeds, because
+     * ap_should_be_on() returns true unconditionally when no STA is
+     * configured. (Reproduced 2026-05-07 on a freshly-erased C3.) */
+    s_net.sta_configured = true;
 
     /* AP keeps running throughout. Just retarget STA. */
     esp_wifi_disconnect();