Encoding/Interpretation of kiwix-serve parameter seems wrong

[kelson42]

Reported at kiwix/kiwix-android#4954 (comment)

Here we search for D&D, and the server returns this result.

Here I have searched for the encoded one D%26D and it is showing the D&D files.

[kelson42]

To me it seems we go through a double decoding here... which breaks the feature. This should be carefully and fully unit tested.