🎨 UI Improvements

[kra-mo]

cc @jancborchardt

For whatever reason

A sub-issue must belong to the same organization or user as the parent.

so here are the ones in nextcloud-vue:

• [NcAppContent + NcAppNavigationItem + NcListItem] Revise styling nextcloud-libraries/nextcloud-vue#7222
• [NcButton] Add a slight shadow to buttons nextcloud-libraries/nextcloud-vue#7220
• [NcFields] Adjust border styling nextcloud-libraries/nextcloud-vue#7221
• [Meta] Forms design improvement nextcloud-libraries/nextcloud-vue#7124
• New input styles for input like elements nextcloud-libraries/nextcloud-vue#7386