Feature/v2/filewithid implementation (#4369)

Added Filewithid type
Updated code where file was being used to use filewithid
Updated places we identified files by name or composite keys to use UUID
Updated places we should have been using quickkey
Updated pageeditor issue where we parsed pagenumber from pageid instead
of using pagenumber directly

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: James Brunton <jbrunton96@gmail.com>

frontend/src/utils/fileIdSafety.ts

@@ -0,0 +1,14 @@
+/**
+ * Runtime validation utilities for FileId safety
+ */
+
+import { FileId } from '../types/fileContext';
+
+// Validate that a string is a proper FileId (has UUID format)
+export function isValidFileId(id: string): id is FileId {
+  // Check UUID v4 format: 8-4-4-4-12 hex digits
+  const uuidRegex = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+  return uuidRegex.test(id);
+}
+
+