[FIX] ESP32 Ethernet: make NetworkAdvancedSetup work, and skip WiFiManager when Ethernet is up (#2351)

Static IP over Ethernet on ESP32 was unusable, and a fresh board with a
working Ethernet link still brought up the WiFi radio.

setup_ethernet_esp32() did not compile with NetworkAdvancedSetup defined: it
declared ip_adress/gateway_adress/subnet_adress/dns_adress but then called
fromString() on ip/gateway/subnet/Dns, which are declared nowhere. The WiFi
path a few hundred lines above does the same thing correctly, so this looks
like an incomplete copy of it.

Once that compiles, the static IP was still ignored. ETH.config() was called
before ETH.begin(), but NetworkInterface::config() returns false immediately
while _esp_netif is NULL, and the netif is only created inside begin(). The
call was a silent no-op and the board kept asking for DHCP. Swapping the order
is safe: the client branch of config() stops the running DHCP client itself
and sets the static-IP status bit. The return value is now checked and logged
instead of being discarded.

Separately, the "no config in flash" branch of setup() called
setupWiFiManager() guarded only by !failSafeMode, while the "config loaded"
branch a few lines above correctly also checks !ethConnected. So a
factory-fresh board with Ethernet already up would still start the WiFi
manager. Beyond being unnecessary, it powers up the 2.4GHz radio and competes
with BLE on gateways that run both.

Verified on an Olimex ESP32-POE-ISO: the board now takes its static address
immediately with no DHCP wait, does not fall back to the WiFi manager, and
reaches the broker. Formatting checked with clang-format against .clang-format.

main/main.cpp

@@ -1451,9 +1451,13 @@ void setup() {
     checkSerial();
 #  endif
 
-    THEENGS_LOG_NOTICE(F("No config in flash, launching wifi manager" CR));
-    // In failSafeMode we don't want to setup wifi manager as it has already been done before
-    if (!failSafeMode) setupWiFiManager();
+    // In failSafeMode we don't want to setup wifi manager as it has already been done before,
+    // and with Ethernet already connected we don't need it at all: bringing up the WiFi radio
+    // would only add 2.4GHz contention with BLE.
+    if (!failSafeMode && !ethConnected) {
+      THEENGS_LOG_NOTICE(F("No config in flash, launching wifi manager" CR));
+      setupWiFiManager();
+    }
   }
 
 #endif
@@ -2447,18 +2451,23 @@ void setup_ethernet_esp32() {
   bool ethBeginSuccess = false;
   WiFi.onEvent(WiFiEvent);
 #    ifdef NetworkAdvancedSetup
-  IPAddress ip_adress;
-  IPAddress gateway_adress;
-  IPAddress subnet_adress;
-  IPAddress dns_adress;
-  ip.fromString(NET_IP);
-  gateway.fromString(NET_GW);
-  subnet.fromString(NET_MASK);
-  Dns.fromString(NET_DNS);
-
   THEENGS_LOG_TRACE(F("Adv eth cfg" CR));
-  ETH.config(ip, gateway, subnet, Dns);
+  // ETH.config() has to be called after ETH.begin(): the underlying netif is
+  // created by begin(), before that the call returns false and is a no-op.
   ethBeginSuccess = ETH.begin();
+  if (ethBeginSuccess) {
+    IPAddress ip_adress;
+    IPAddress gateway_adress;
+    IPAddress subnet_adress;
+    IPAddress dns_adress;
+    ip_adress.fromString(NET_IP);
+    gateway_adress.fromString(NET_GW);
+    subnet_adress.fromString(NET_MASK);
+    dns_adress.fromString(NET_DNS);
+    if (!ETH.config(ip_adress, gateway_adress, subnet_adress, dns_adress)) {
+      THEENGS_LOG_ERROR(F("Adv eth cfg failed" CR));
+    }
+  }
 #    else
   THEENGS_LOG_NOTICE(F("Spl eth cfg" CR));
   ethBeginSuccess = ETH.begin();