fix(mqtt): honour mqtt.status off for the on-connect status message

Only the periodic status path consulted the setting. The connect callback armed
a status publish unconditionally and publishStatusToSlot() never checked it, so
every boot and every reconnect published a status message — including the
metadata an operator turned the setting off to suppress. The documented contract
is "Enable/disable status messages".

Read the toggle live from prefs at publish time, matching the periodic path, and
also skip a slot the operator has disabled: teardown only stops a client that
reports connected, so a slot switched off mid-connect can still complete its
handshake and arm this publish.

MQTT_IMPLEMENTATION.md

@@ -531,7 +531,7 @@ These settings apply across all MQTT slots:
 #### Set Commands
 - `set mqtt.origin <name>` - Set device origin name
 - `set mqtt.iata <code>` - Set IATA code (auto-uppercased)
-- `set mqtt.status on|off` - Enable/disable status messages
+- `set mqtt.status on|off` - Enable/disable status messages (periodic *and* the one sent on each broker connect)
 - `set mqtt.packets on|off` - Enable/disable packet messages
 - `set mqtt.raw on|off` - Enable/disable raw messages
 - `set mqtt.rx on|off` - Enable/disable RX (received) packet uplinking

src/helpers/bridges/MQTTBridge.cpp

@@ -2604,6 +2604,16 @@ void MQTTBridge::publishStatusToSlot(int index) {
   if (index < 0 || index >= RUNTIME_MQTT_SLOTS) return;
   MQTTSlot& slot = _slots[index];
   if (!slot.client || !slot.connected) return;
+  // `set mqtt.status off` disables status messages, on-connect ones included
+  // (MQTT_IMPLEMENTATION.md: "Enable/disable status messages"). Read live from
+  // prefs like the periodic path, and checked here rather than at the pending
+  // flag so the setting that counts is the one in force when we publish.
+  if (!_obs->mqtt_status_enabled) return;
+  // A disabled slot can still hold a connection that was established before it
+  // was switched off (teardown only stops a client reporting connected), and
+  // its callback arms this publish. Do not speak for a slot the operator
+  // turned off.
+  if (!slot.enabled) return;
 
   refreshOriginFromPrefs();