[ZEPPELIN-6202] Fix %20 showing in notebook tree by URL-decoding note file paths

[ParkGyeongTae]

What is this PR for?

This PR fixes a UI bug where notebook and folder names that contain spaces are displayed with the URL-encoded text %20 in the notebook tree (e.g., Flink%20Tutorial). We now URL-decode the VFS path and keep the existing Windows-specific prefix handling, so names with spaces render correctly across all platforms.

What type of PR is it?

Bug Fix

Todos

• [x] - Add URL-decode logic in path normalisation

What is the Jira issue?

• Jira: https://issues.apache.org/jira/browse/ZEPPELIN/ZEPPELIN-6202

How should this be tested?

• Build this branch and start Zeppelin.
• Create or import a notebook whose name contains a space (e.g., “Python Tutorial”).

Screenshots (if appropriate)

Before After

Questions:

• Does the license files need to update? No.
• Is there breaking changes for older versions? No.
• Does this needs documentation? No.