fix: Fix drag and drop file upload functionality

Resolve issue where dragging and dropping files into the dropzone
did not trigger the file input change event properly.

Changed from sp-dropzone custom events to native HTML5 drag and drop
events (dragover, dragenter, drop) since sp-dropzone component is
no longer used. Use DataTransfer to create a new FileList and assign
it to enable proper file selection via drag and drop.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: SimYunSup

src/DotNetDevLottery/typescript/Pages/Main.r.ts

@@ -3,13 +3,31 @@ export function clickElement(element: HTMLElement) {
 }
 
 export function addDropEventToChangeInputFile(element: HTMLElement) {
-  element.addEventListener('sp-dropzone-drop', (e) => {
-    const event = e as CustomEvent<DragEvent>;
+  // Prevent default drag behaviors
+  element.addEventListener('dragover', (e) => {
+    e.preventDefault();
+    e.stopPropagation();
+  });
+
+  element.addEventListener('dragenter', (e) => {
+    e.preventDefault();
+    e.stopPropagation();
+  });
+
+  // Handle drop event
+  element.addEventListener('drop', (e) => {
+    e.preventDefault();
+    e.stopPropagation();
+
     const targetInputElement: HTMLInputElement | null = element.querySelector("input[type='file']");
-    if(event.detail.dataTransfer?.files && targetInputElement) {
-      targetInputElement.files = event.detail.dataTransfer.files;
-      const changeEvent = new Event('change')
-      targetInputElement?.dispatchEvent(changeEvent);
+    if(e.dataTransfer?.files && targetInputElement) {
+      const dt = new DataTransfer();
+      Array.from(e.dataTransfer.files).forEach(file => {
+        dt.items.add(file);
+      });
+      targetInputElement.files = dt.files;
+      const changeEvent = new Event('change', { bubbles: true })
+      targetInputElement.dispatchEvent(changeEvent);
     }
-  })
+  });
 }