Added new class `flex-container-sidebar` to cover the dashboard sidebar.
Previously this was 37.5% with more padding. Now there is less empty
space between the two columns and this matches other pages like repo or
admin settings page.
Desktop:
<img width="1345" alt="Screenshot 2024-03-31 at 15 11 36"
src="https://github.com/go-gitea/gitea/assets/115237/717389d9-d42c-466e-a8fe-e968f79447fd">
Mobile:
<img width="444" alt="Screenshot 2024-03-31 at 15 11 44"
src="https://github.com/go-gitea/gitea/assets/115237/7faa840b-513a-411b-bf2d-26d52b9b71a0">
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Co-authored-by: Giteabot <teabot@gitea.io>
(cherry picked from commit 044cc169e75dccbf1d846f8774ef2feccd0da1fd)
d8258482e2