Fix mobile navbar and misc cleanups (#25134) (#25169)

Backport #25134 by @silverwind

- Fix and improve mobile navbar layout
- Apply all cleanups suggested in
https://github.com/go-gitea/gitea/pull/25111
- Make media query breakpoints match Fomantic's exactly
- Clean up whitespace in class on navbar items

Mobile navbar before and after:
<img width="745" alt="Screenshot 2023-06-08 at 08 40 56"
src="https://github.com/go-gitea/gitea/assets/115237/ca84b239-b10f-41db-8c06-dcf2b6dd9d28">
<img width="739" alt="Screenshot 2023-06-08 at 08 41 23"
src="https://github.com/go-gitea/gitea/assets/115237/09133c54-eb7e-4110-858c-ead23c3b7521">

templates/repo/settings/lfs_file_find.tmpl

@@ -29,7 +29,6 @@
 										<a class="ui primary sha label" href="{{$.RepoLink}}/commit/{{.String}}">{{ShortSha .String}}</a>
 									{{end}}
 								{{end}}
-								<div class="mobile-only"></div>
 								{{$.locale.Tr "repo.diff.commit"}}
 								<a class="ui primary sha label" href="{{$.RepoLink}}/commit/{{.SHA}}">{{ShortSha .SHA}}</a>
 							</td>