Fix GPS +8mA power leak: assert reset pin in stop()

Root cause: MicroNMEALocationProvider::stop() was not asserting the
reset pin. On boards like the Heltec T114 where GPS_RESET (pin 38) is
the same as PIN_3V3_EN, begin() sets pin 38 HIGH (powering the 3V3
rail) but stop() never set it back LOW. This left the GPS module
powered even when disabled, causing +8mA constant draw.

Also reverts previous Serial1.end()/PSEL workaround attempts - the
UART hang was a symptom of the GPS still being powered and sending
NMEA data, not the root cause.

Adds gps_active guard on _location->loop() to avoid processing NMEA
data when GPS is disabled.

Fixes #1628

Author: weebl2000

src/helpers/sensors/EnvironmentSensorManager.cpp

@@ -583,14 +583,6 @@ void EnvironmentSensorManager::initBasicGPS() {
     MESH_DEBUG_PRINTLN("No GPS detected");
   }
   _location->stop();
-#ifdef NRF52_PLATFORM
-  // Redirect UART RX to its own TX pin before ending Serial. When GPS powers
-  // down its TX drops LOW (break condition), preventing nRF52 UARTE's RXTO
-  // event from firing and hanging Serial1.end() indefinitely. Looping RX to
-  // TX guarantees an idle (HIGH) line so RXTO fires promptly.
-  NRF_UARTE0->PSEL.RXD = NRF_UARTE0->PSEL.TXD;
-#endif
-  Serial1.end();  // Disable UART peripheral to save power (significant on nRF52)
   gps_active = false; //Set GPS visibility off until setting is changed
 }
 
@@ -688,14 +680,6 @@ void EnvironmentSensorManager::start_gps() {
     return;
   #endif
 
-  // Re-initialize UART (was closed by stop_gps() to save power)
-  Serial1.setPins(PIN_GPS_TX, PIN_GPS_RX);
-  #ifdef GPS_BAUD_RATE
-  Serial1.begin(GPS_BAUD_RATE);
-  #else
-  Serial1.begin(9600);
-  #endif
-
   _location->begin();
   _location->reset();
 
@@ -713,11 +697,6 @@ void EnvironmentSensorManager::stop_gps() {
   #endif
 
   _location->stop();
-#ifdef NRF52_PLATFORM
-  // Redirect UART RX to TX pin — see comment in initBasicGPS()
-  NRF_UARTE0->PSEL.RXD = NRF_UARTE0->PSEL.TXD;
-#endif
-  Serial1.end();  // Disable UART peripheral to save power (significant on nRF52)
 
   #ifndef PIN_GPS_EN
   MESH_DEBUG_PRINTLN("Stop GPS is N/A on this board. Actual GPS state unchanged");

src/helpers/sensors/MicroNMEALocationProvider.h

@@ -79,7 +79,10 @@ public :
         if (_pin_en != -1) {
             digitalWrite(_pin_en, !PIN_GPS_EN_ACTIVE);
         }
-        if (_peripher_power) _peripher_power->release();  
+        if (_pin_reset != -1) {
+            digitalWrite(_pin_reset, GPS_RESET_FORCE);
+        }
+        if (_peripher_power) _peripher_power->release();
     }
 
     bool isEnabled() override {