Change error message from '50 carroll not found' to 'Invalid File type'

app.py

@@ -1333,7 +1333,7 @@ def compare_pdfs(file_a, file_b):
 
         # Check for "50 carroll" text in both files
         if not _contains_50_carroll(file_a.name) or not _contains_50_carroll(file_b.name):
-            return None, None, None, "❌ Invalid File - Required text '50 carroll' not found", [], []
+            return None, None, None, "❌ Invalid File type", [], []
 
         # Load images with multiple pages support
         pages_a = load_pdf_pages(file_a.name, dpi=600, max_pages=15)