v1.1.2: Smooth HR variation, validation, and UI improvements

- Fix HR variation to use smooth sinusoidal algorithm instead of erratic jumps
- Clamp HR values to ±3 of target (was exceeding bounds)
- Add Pydantic Field validation for device values in API
- Add runtime BPM validation in MCP server
- Add battery slider control for HR monitor
- Add distance display and reset button for treadmill
- Add UI/API version display in header
- Firmware: web portal improvements, battery/distance controls

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

firmware/esp32_ble_sim/include/ble_services.h

@@ -12,6 +12,10 @@
 #define HEART_RATE_MEASUREMENT_UUID    "2A37"
 #define BODY_SENSOR_LOCATION_UUID      "2A38"
 
+// Battery Service
+#define BATTERY_SERVICE_UUID           "180F"
+#define BATTERY_LEVEL_UUID             "2A19"
+
 // Fitness Machine Service
 #define FITNESS_MACHINE_SERVICE_UUID   "1826"
 #define TREADMILL_DATA_UUID            "2ACD"
@@ -49,11 +53,18 @@ void setupBLE_Treadmill();
  */
 void notifyHeartRate(uint8_t bpm);
 
+/**
+ * Update battery level
+ * @param level Battery level 0-100%
+ */
+void updateBatteryLevel(uint8_t level);
+
 /**
  * Send treadmill data notification
  * @param speed Speed in 0.01 km/h units
  * @param incline Incline in 0.1% units
+ * @param distance Total distance in meters
  */
-void notifyTreadmill(uint16_t speed, int16_t incline);
+void notifyTreadmill(uint16_t speed, int16_t incline, uint32_t distance);
 
 #endif // BLE_SERVICES_H