refactor(io): unique_ptr ownership for motion sensors and I2C keyboard (#11458)

* refactor(io): unique_ptr ownership for motion sensors and I2C keyboard

- AccelerometerThread / MagnetometerThread: the owned MotionSensor
  becomes unique_ptr, removing the manual delete/null bookkeeping in
  clean(). Deletion behavior is unchanged (MotionSensor's destructor is
  virtual).

- KbI2cBase: the TCA keyboard was a reference member bound to an
  anonymous heap allocation - ownership was invisible and nothing could
  ever free it. It becomes unique_ptr with an out-of-line destructor
  (the base type is only forward-declared in the header).

- GeoCoord::pointAtDistance returned shared_ptr with no shared
  ownership anywhere (and no callers); return by value instead.

No behavior change.

* fix(io): make TCA8418KeyboardBase destructor public for unique_ptr ownership

* refactor(gps): delete dead pointAtDistance instead of converting it

Per review: zero callers in this repo or device-ui, and the math was
wrong at both ends (rangeMetersToRadians multiplies meters by 1852,
treating meters as nautical miles). Remove it, its now-unused helper,
and the <memory> include the old shared_ptr signature pulled in.

src/motion/AccelerometerThread.h

@@ -21,6 +21,8 @@
 #include "LSM6DS3Sensor.h"
 #include "MPU6050Sensor.h"
 #include "MotionSensor.h"
+
+#include <memory>
 #ifdef HAS_QMA6100P
 #include "QMA6100PSensor.h"
 #endif
@@ -33,7 +35,7 @@ extern ScanI2C::DeviceAddress accelerometer_found;
 class AccelerometerThread : public concurrency::OSThread
 {
   private:
-    MotionSensor *sensor = nullptr;
+    std::unique_ptr<MotionSensor> sensor;
     bool isInitialised = false;
 
   public:
@@ -93,56 +95,56 @@ class AccelerometerThread : public concurrency::OSThread
         switch (device.type) {
 #ifdef HAS_BMA423
         case ScanI2C::DeviceType::BMA423:
-            sensor = new BMA423Sensor(device);
+            sensor.reset(new BMA423Sensor(device));
             break;
 #endif
 #if __has_include(<Adafruit_MPU6050.h>)
         case ScanI2C::DeviceType::MPU6050:
-            sensor = new MPU6050Sensor(device);
+            sensor.reset(new MPU6050Sensor(device));
             break;
 #endif
         case ScanI2C::DeviceType::BMX160:
-            sensor = new BMX160Sensor(device);
+            sensor.reset(new BMX160Sensor(device));
             break;
 #if __has_include(<Adafruit_LIS3DH.h>)
         case ScanI2C::DeviceType::LIS3DH:
         case ScanI2C::DeviceType::SC7A20:
-            sensor = new LIS3DHSensor(device);
+            sensor.reset(new LIS3DHSensor(device));
             break;
 #endif
 #if __has_include(<Adafruit_LSM6DS3TRC.h>)
         case ScanI2C::DeviceType::LSM6DS3:
-            sensor = new LSM6DS3Sensor(device);
+            sensor.reset(new LSM6DS3Sensor(device));
             break;
 #endif
 #ifdef HAS_STK8XXX
         case ScanI2C::DeviceType::STK8BAXX:
-            sensor = new STK8XXXSensor(device);
+            sensor.reset(new STK8XXXSensor(device));
             break;
 #endif
 #if __has_include(<ICM_20948.h>)
         case ScanI2C::DeviceType::ICM20948:
-            sensor = new ICM20948Sensor(device);
+            sensor.reset(new ICM20948Sensor(device));
             break;
 #endif
 #if __has_include(<ICM42670P.h>)
         case ScanI2C::DeviceType::ICM42607P:
-            sensor = new ICM42607PSensor(device);
+            sensor.reset(new ICM42607PSensor(device));
             break;
 #endif
 #if __has_include(<DFRobot_BMM150.h>)
         case ScanI2C::DeviceType::BMM150:
-            sensor = new BMM150Sensor(device);
+            sensor.reset(new BMM150Sensor(device));
             break;
 #endif
 #ifdef HAS_BMI270
         case ScanI2C::DeviceType::BMI270:
-            sensor = new BMI270Sensor(device);
+            sensor.reset(new BMI270Sensor(device));
             break;
 #endif
 #ifdef HAS_QMA6100P
         case ScanI2C::DeviceType::QMA6100P:
-            sensor = new QMA6100PSensor(device);
+            sensor.reset(new QMA6100PSensor(device));
             break;
 #endif
         default:
@@ -185,8 +187,7 @@ class AccelerometerThread : public concurrency::OSThread
     void clean()
     {
         isInitialised = false;
-        delete sensor;
-        sensor = nullptr;
+        sensor.reset();
     }
 };