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/apps/slave_node/boards/weact_stm32g431_core.overlay

@@ -23,22 +23,22 @@
     pinctrl-names = "default";
 };
 
-&adc1 { // ADC1 wird für PA0 verwendet
-    status = "okay"; // ADC1 aktivieren
-    pinctrl-0 = <&adc1_in1_pa0>; // Pinmux für PA0 als ADC1_IN1
+&adc1 {
+    status = "okay";
+    pinctrl-0 = <&adc1_in1_pa0>;
     pinctrl-names = "default";
     st,adc-clock-source = "SYNC";
     st,adc-prescaler = <4>;
     #address-cells = <1>;
     #size-cells = <0>;
 
-    // Definition des ADC-Kanals für MULTISENSE (PA0)
-    channel@1 { // ADC1_IN1 ist Kanal 1
-        reg = <1>; // Kanalnummer
+    channel@1 {
+        reg = <1>;
         zephyr,gain = "ADC_GAIN_1";
         zephyr,reference = "ADC_REF_INTERNAL";
         zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
         zephyr,resolution = <12>;
+        zephyr,vref-mv = <3300>;
     };
 };