Add GPS support Heltec Wireless Tracker v1.x

Pin mapping verified against HTIT-Tracker V0.5 schematic:
- GPIO35 (GPS_EN): N-ch MOSFET drives P-ch high-side switch, active HIGH
- GPIO36 (GPS_RST): hardware reset, active LOW
- GPIO33/34: UART TX/RX

Delegates power management to MicroNMEALocationProvider begin()/stop()
which independently controls GPS power via GPS_EN and shares VEXT with
the display through RefCountedDigitalPin.

variants/heltec_tracker/platformio.ini

@@ -32,6 +32,11 @@ build_flags =
   -D PIN_TFT_LEDA_CTL=21     ; LEDK (switches on/off via mosfet to create the ground)
   -D PIN_GPS_RX=33
   -D PIN_GPS_TX=34
+  -D PIN_GPS_EN=35              ; N-ch MOSFET Q2 drives P-ch high-side switch → active HIGH (default)
+  -D PIN_GPS_RESET=36
+  -D PIN_GPS_RESET_ACTIVE=LOW
+  -D GPS_BAUD_RATE=115200
+  -D ENV_INCLUDE_GPS=1
   -D SX126X_DIO2_AS_RF_SWITCH=true
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140

variants/heltec_tracker/target.cpp

@@ -16,7 +16,8 @@ WRAPPER_CLASS radio_driver(radio, board);
 
 ESP32RTCClock fallback_clock;
 AutoDiscoverRTCClock rtc_clock(fallback_clock);
-MicroNMEALocationProvider nmea = MicroNMEALocationProvider(Serial1);
+// GPS_EN (GPIO35) drives N-ch MOSFET → P-ch high-side switch; GPS_RESET (GPIO36) active LOW
+MicroNMEALocationProvider nmea = MicroNMEALocationProvider(Serial1, &rtc_clock, GPS_RESET, GPS_EN, &board.periph_power);
 HWTSensorManager sensors = HWTSensorManager(nmea);
 
 #ifdef DISPLAY_CLASS
@@ -58,18 +59,16 @@ mesh::LocalIdentity radio_new_identity() {
 
 void HWTSensorManager::start_gps() {
   if (!gps_active) {
-    board.periph_power.claim();
+    _location->begin();  // Claims periph_power via RefCountedDigitalPin
-
     gps_active = true;
-    Serial1.println("$CFGSYS,h35155*68");
+    Serial1.println("$CFGSYS,h35155*68");  // Configure GPS for all constellations
   }
 }
 
 void HWTSensorManager::stop_gps() {
   if (gps_active) {
     gps_active = false;
-
+    _location->stop();  // Releases periph_power via RefCountedDigitalPin
-    board.periph_power.release();
   }
 }
 

variants/heltec_tracker/target.h

@@ -28,6 +28,7 @@ public:
   const char* getSettingName(int i) const override;
   const char* getSettingValue(int i) const override;
   bool setSettingValue(const char* name, const char* value) override;
+  LocationProvider* getLocationProvider() override { return _location; }
 };
 
 extern HeltecV3Board board;