Implement VND7050AJ supply voltage reading function

- Added devicetree overlay for VND7050AJ with GPIO and ADC configuration
- Created custom devicetree binding for VND7050AJ valve controller
- Implemented valve_get_supply_voltage() function with proper pin control:
  - RST=HIGH to enable VND7050AJ
  - S0=1, S1=1 for supply voltage sensing mode
  - SEN=1 to enable MULTISENSE output
  - ADC reading on PA0 (ADC1_IN1) with 12-bit resolution
- Fixed supply voltage calculation (VCC/8 per datasheet)
- Added comprehensive debug logging for all steps
- Tested and verified ADC functionality
- Current reading: 5.1V (may be limited by hardware power supply)

Files modified:
- software/lib/valve/valve.c: Main implementation
- software/apps/slave_node/boards/weact_stm32g431_core.overlay: DT config
- software/apps/slave_node/dts/bindings/vnd7050aj-valve-controller.yaml: DT binding
- software/apps/slave_node/src/main.c: Test code
- software/apps/slave_node/prj.conf: ADC driver enablement

software/serial_monitor.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+import serial
+import time
+import sys
+
+def monitor_serial():
+    try:
+        # Open serial connection
+        ser = serial.Serial('/dev/ttyACM3', 115200, timeout=1)
+        print("Connected to /dev/ttyACM3")
+        
+        # Send reset command
+        ser.write(b'reset\n')
+        print("Sent reset command")
+        
+        # Wait a bit and then read output
+        time.sleep(0.5)
+        
+        # Read output for 10 seconds
+        start_time = time.time()
+        while time.time() - start_time < 10:
+            if ser.in_waiting > 0:
+                data = ser.read(ser.in_waiting)
+                try:
+                    text = data.decode('utf-8', errors='ignore')
+                    print(text, end='')
+                except:
+                    print(f"Raw bytes: {data}")
+            time.sleep(0.1)
+        
+        ser.close()
+        print("\nSerial monitor closed")
+        
+    except Exception as e:
+        print(f"Error: {e}")
+        sys.exit(1)
+
+if __name__ == "__main__":
+    monitor_serial()