Refactor expense form and categories

-   Rename "지출 추가" to "지출 입력" in the add expense dialog.
-   Rename "교통비" to "교통" in categories and ensure all 4 icons are displayed on a single line.

src/components/expenses/ExpenseCategorySelector.tsx

@@ -17,7 +17,7 @@ const ExpenseCategorySelector: React.FC<ExpenseCategorySelectorProps> = ({
     <FormControl>
       <ToggleGroup 
         type="single" 
-        className="justify-start flex-wrap gap-2"
+        className="justify-between flex-nowrap gap-1"
         value={value}
         onValueChange={(value) => {
           if (value) onValueChange(value);
@@ -27,7 +27,7 @@ const ExpenseCategorySelector: React.FC<ExpenseCategorySelectorProps> = ({
           <ToggleGroupItem 
             key={category} 
             value={category}
-            className="px-4 py-2 rounded-md border flex items-center gap-2"
+            className="px-3 py-2 rounded-md border flex items-center gap-1"
           >
             <div className="text-neuro-income">
               {categoryIcons[category]}