Fix encoding for file tree browser paths with special characters

What does this MR do and why?

Ensure file and directory paths containing spaces and special characters are properly encoded when generating router paths

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Create a new branch with special characters in the name (e.g., !@#$%/)(&())
2. In this branch, create a directory with special characters (e.g., @#$%^&*rthsi^%)
3. Inside that directory, create files with special characters in their names (e.g., test_*^%.js).
4. Navigate to Repository > Files in the GitLab UI
5. Browse to the directory with special characters
6. Click on files with special characters in the file tree browser (left sidebar)
7. Expected: Files should load correctly

MR acceptance checklist

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Related to #581015 (closed)