Fix build errors for ESP8266 and PICOW platforms

- Replace aggregate initializers with memset for ESP8266 compatibility
- Add platform guards for PICOW boards that lack baudRate() method
- Use default 9600 baud for PICOW GPS initialization

Author: brentru

src/components/gps/hardware.cpp

@@ -357,7 +357,12 @@ bool GPSHardware::DetectMtkUart() {
 
   // Attempt to use Adafruit_GPS
   _ada_gps = new Adafruit_GPS(_hw_serial);
+#if defined(ARDUINO_RASPBERRY_PI_PICO_W) || defined(ARDUINO_RASPBERRY_PI_PICO_2W)
+  // PICOW doesn't have baudRate() method, use default baud
+  if (!_ada_gps->begin(9600)) {
+#else
   if (!_ada_gps->begin(_hw_serial->baudRate())) {
+#endif
     WS_DEBUG_PRINTLN("[gps] ERROR: Failed to initialize Mediatek!");
     return false;
   }

src/components/gps/model.cpp

@@ -122,7 +122,7 @@ bool GPSModel::AddGpsEventRMC(wippersnapper_gps_GPSDateTime datetime,
 
   // Always store at index 0, overwriting any previous response
   wippersnapper_gps_GPSRMCResponse rmc_response;
-  rmc_response = wippersnapper_gps_GPSRMCResponse_init_zero;
+  memset(&rmc_response, 0, sizeof(rmc_response));
   rmc_response.has_datetime = true;
   rmc_response.datetime = datetime;