feat: add simple stall detection with threshold + debounce

- Add STALL_THRESHOLD (8A) and STALL_CONFIRM_SAMPLES (3) config
- Add 500ms stabilization delay after direction change to prevent false positives
- Add stall warning banner in web UI
- Stop motor and pingpong when stall detected

Algorithm: If active current > 8A for 3 consecutive samples (300ms),
and motor has been running for at least 500ms, trigger stall callback.

include/config.h

@@ -40,6 +40,12 @@
 // Current logging interval for data collection
 #define CURRENT_LOG_INTERVAL_MS 100  // Log current readings every 100ms
 
+// Simple Stall Detection
+// Based on clean data: Running ~2A, Stall ~17A (8.5x difference)
+#define STALL_THRESHOLD 8.0f          // Amps - midpoint between 2A run and 17A stall
+#define STALL_CONFIRM_SAMPLES 3       // Debounce: 3 samples = 300ms at 100ms interval
+#define STALL_STABILIZE_MS 500        // Ignore current spikes for 500ms after direction change
+
 // Web Server
 #define HTTP_PORT 80
 

include/motor.h

@@ -4,6 +4,9 @@
 #include <Arduino.h>
 #include "config.h"
 
+// Stall callback function type
+typedef void (*StallCallback)();
+
 class MotorController {
 public:
     void begin();
@@ -18,6 +21,11 @@ public:
     float getCurrentLeft();          // Current in amps (reverse direction)
     float getCurrentActive();        // Current from active direction
     
+    // Stall detection
+    bool isStalled();
+    void setStallCallback(StallCallback callback);
+    void resetStallDetection();
+    
     // Pingpong mode (time-based only)
     void startPingpong(int speed, int timeMs, int speedRandomPercent, int timeRandomPercent);
     void stopPingpong();
@@ -48,11 +56,18 @@ private:
     unsigned long _pingpongLastSwitch = 0;
     int _pingpongDirection = 1;
     
+    // Stall detection state
+    bool _stalled = false;
+    int _stallConfirmCount = 0;
+    StallCallback _stallCallback = nullptr;
+    unsigned long _lastDirectionChangeTime = 0;
+    
     void applyMotorState();
     float readCurrentSense(int pin);
     void calibrateCurrentOffset();
     void updatePingpong();
     int applyRandomness(int baseValue, int randomPercent);
+    void checkStall();
 };
 
 extern MotorController motor;