Remove pingpong mode completely

- Remove pingpong method declarations and member variables from motor.h
- Remove pingpong implementation (startPingpong, stopPingpong, updatePingpong, etc.) from motor.cpp
- Remove pingpong UI section, handlers, and routes from webserver.cpp
- Remove stopPingpong call from stall callback in main.cpp

include/motor.h

@@ -26,15 +26,6 @@ public:
     void setStallCallback(StallCallback callback);
     void resetStallDetection();
     
-    // Pingpong mode (time-based only)
-    void startPingpong(int speed, int timeMs, int speedRandomPercent, int timeRandomPercent);
-    void stopPingpong();
-    bool isPingpongActive();
-    int getPingpongSpeed();
-    int getPingpongTime();
-    int getPingpongSpeedRandom();
-    int getPingpongTimeRandom();
-
 private:
     int _speed = 0;
     int _direction = 0;
@@ -45,17 +36,6 @@ private:
     int _adcOffsetRight = 0;
     int _adcOffsetLeft = 0;
     
-    // Pingpong state
-    bool _pingpongActive = false;
-    int _pingpongBaseSpeed = 50;
-    int _pingpongBaseTime = 2000;
-    int _pingpongSpeedRandomPercent = 0;
-    int _pingpongTimeRandomPercent = 0;
-    int _pingpongCurrentSpeed = 50;
-    int _pingpongCurrentTime = 2000;
-    unsigned long _pingpongLastSwitch = 0;
-    int _pingpongDirection = 1;
-    
     // Stall detection state
     bool _stalled = false;
     int _stallConfirmCount = 0;
@@ -65,8 +45,6 @@ private:
     void applyMotorState();
     float readCurrentSense(int pin);
     void calibrateCurrentOffset();
-    void updatePingpong();
-    int applyRandomness(int baseValue, int randomPercent);
     void checkStall();
 };