Add coordinated homing for both motors with toggle button

- Add state machine for coordinated movement (REV/FWD toggle)
- Each motor stops independently on stall detection
- Add HOME BOTH button in web UI with state-based styling
- Add /homing endpoint for programmatic control
- Update /status endpoint with coordinated state info
- Create homing.h header for function declarations

include/homing.h

@@ -0,0 +1,10 @@
+#ifndef HOMING_H
+#define HOMING_H
+
+// Coordinated movement functions (defined in main.cpp)
+int toggleCoordinatedMovement(int speed);
+void stopCoordinatedMovement();
+int getCoordinatedState();
+bool isCoordinatedMovementDone();
+
+#endif