feat(AppDataSearch): add customizable placeholder prop

### Summary
This PR introduces a `placeholder` prop to the `AppDataSearch` component, allowing consumers to define custom placeholder text instead of using the hardcoded "Search".

### Changes
- Added `placeholder` prop with default value `"Search"`
- Updated template to use `:placeholder="placeholder"` instead of `__('Search')`
- Maintains backward compatibility (defaults to `"Search"` if no prop is passed)

### Usage Example
```vue
<AppDataSearch
    :url="route('student.index')"
    fields-to-search="name"
    placeholder="Search by student name"
></AppDataSearch>

Author: mehedijaman

stubs/resources/js/Components/DataTable/AppDataSearch.vue

@@ -8,7 +8,7 @@
             <AppInputText
                 id="search"
                 v-model="searchTerm"
-                :placeholder="__('Search')"
+                :placeholder="placeholder"
                 name="search"
                 class="w-full py-2 pl-9 md:w-1/2"
             ></AppInputText>
@@ -39,6 +39,10 @@ const props = defineProps({
     additionalParams: {
         type: Object,
         default: () => {}
+    },
+     placeholder: {
+        type: String,
+        default: 'Search'
     }
 })