🐛(components): add missing button types and keys

Add type="button" to the EditMobility and UploadStudents buttons
to prevent default form submission behavior.
Include a key prop on Student components in Promotion for stable list rendering.

routes/(apps)/students/(_islands)/UploadStudents.tsx

@@ -104,7 +104,7 @@ export default function UploadStudents() {
   return (
     <>
       <input type="file" accept=".xlsx, .xls" onChange={handleFileChange} />
-      <button onClick={confirmUpload}>Confirm Upload</button>
+      <button type="button" onClick={confirmUpload}>Confirm Upload</button>
       <p>{statusMessage.value}</p>
     </>
   );