fix: Improve number and slider input handling in V2Input and SplitPanelLayoutComponent

- Enhanced V2Input to convert string values from the database to numbers for number and slider inputs, ensuring correct display and functionality.
- Updated primary key retrieval logic in SplitPanelLayoutComponent to prioritize actual DB id values, improving data integrity.
- Simplified primary key handling by removing unnecessary checks and ensuring consistent usage of id fields.
- Improved user feedback in the SplitPanelLayoutComponent with clearer console logs for save operations and item selections.

frontend/components/v2/V2Input.tsx

@@ -771,9 +771,15 @@ export const V2Input = forwardRef<HTMLDivElement, V2InputProps>((props, ref) =>
         );
 
       case "number":
+        // DB에서 문자열("325")로 반환되는 경우도 숫자로 변환하여 표시
+        const numValue = typeof displayValue === "number"
+          ? displayValue
+          : (displayValue !== undefined && displayValue !== null && displayValue !== "" && !isNaN(Number(displayValue)))
+            ? Number(displayValue)
+            : undefined;
         return (
           <NumberInput
-            value={typeof displayValue === "number" ? displayValue : undefined}
+            value={numValue}
             onChange={(v) => {
               setAutoGeneratedValue(null);
               onChange?.(v ?? 0);
@@ -802,9 +808,15 @@ export const V2Input = forwardRef<HTMLDivElement, V2InputProps>((props, ref) =>
         );
 
       case "slider":
+        // DB에서 문자열로 반환되는 경우도 숫자로 변환
+        const sliderValue = typeof displayValue === "number"
+          ? displayValue
+          : (displayValue !== undefined && displayValue !== null && displayValue !== "" && !isNaN(Number(displayValue)))
+            ? Number(displayValue)
+            : (config.min ?? 0);
         return (
           <SliderInput
-            value={typeof displayValue === "number" ? displayValue : (config.min ?? 0)}
+            value={sliderValue}
             onChange={(v) => {
               setAutoGeneratedValue(null);
               onChange?.(v);