added full project files

static/js/validateFileInput.js

@@ -0,0 +1,12 @@
+function validateFileInput() {
+            const fileInput = document.querySelector('input[type="file"]');
+            const filePath = fileInput.value;
+            const allowedExtensions = /(\.xlsx|\.xls)$/i;
+
+            if (!allowedExtensions.exec(filePath)) {
+                alert("Please upload a valid Excel file (.xlsx or .xls only).");
+                fileInput.value = '';
+                return false;
+            }
+            return true;
+        }