Bug: When deleting files or entering folders with multibyte characters, the app might crash

The original issue was reported (along with a PR) here: https://github.com/imsnif/diskonaut/pull/51
This fixes the issue for tiles on the board (the filenames in the rectangle grid), but we would also need to fix this:

error_box
title_telescope
bottom_line

* for folders we enter and the base folder (in the title bar): src/ui/title/title_telescope.rs (I think a change here would suffice: https://github.com/imsnif/diskonaut/blob/120058d81745dbcabfa74a3fbe0f36122ead04a9/src/ui/title/title_telescope.rs#L186)

* for file display in the bottom lines: src/ui/bottom_line.rs (especially in `render_currently_selected` and `render_last_read_path`)

* in deletion confirmation and error message boxes: src/ui/modals/error_box.rs and src/ui/modals/message_box.rs

@goto-bus-stop, I'm assigning this to you since you said you'd like to work on this when you have time. Good catch on these!

Start with the referenced change in src/ui/title/title_telescope.rs around line 186, then inspect render_currently_selected and render_last_read_path in src/ui/bottom_line.rs. Review src/ui/modals/error_box.rs and src/ui/modals/message_box.rs for the deletion and error displays. Done means entering folders, deleting files, and displaying paths with multibyte characters no longer crashes.

Written by the indexing model from the issue text.