dark-mode: Fix background colors of modals and sidebars in mobile view.
dark-mode: Fix background colors of modals and sidebars in mobile view.

Fixes #7623.

kou/zulip,brainwane/zulip,showell/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,jackrzhang/zulip,rishig/zulip,brainwane/zulip,eeshangarg/zulip,showell/zulip,hackerkid/zulip,timabbott/zulip,mahim97/zulip,dhcrzf/zulip,brainwane/zulip,brainwane/zulip,brainwane/zulip,shubhamdhama/zulip,andersk/zulip,mahim97/zulip,rishig/zulip,punchagan/zulip,rht/zulip,jackrzhang/zulip,rht/zulip,mahim97/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,punchagan/zulip,dhcrzf/zulip,zulip/zulip,showell/zulip,rishig/zulip,rishig/zulip,synicalsyntax/zulip,kou/zulip,eeshangarg/zulip,dhcrzf/zulip,rishig/zulip,tommyip/zulip,synicalsyntax/zulip,hackerkid/zulip,kou/zulip,tommyip/zulip,synicalsyntax/zulip,timabbott/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,brainwane/zulip,dhcrzf/zulip,zulip/zulip,tommyip/zulip,shubhamdhama/zulip,andersk/zulip,hackerkid/zulip,shubhamdhama/zulip,dhcrzf/zulip,showell/zulip,shubhamdhama/zulip,jackrzhang/zulip,rht/zulip,zulip/zulip,punchagan/zulip,rht/zulip,shubhamdhama/zulip,jackrzhang/zulip,tommyip/zulip,brainwane/zulip,synicalsyntax/zulip,punchagan/zulip,jackrzhang/zulip,zulip/zulip,mahim97/zulip,kou/zulip,timabbott/zulip,shubhamdhama/zulip,jackrzhang/zulip,synicalsyntax/zulip,andersk/zulip,tommyip/zulip,synicalsyntax/zulip,tommyip/zulip,mahim97/zulip,eeshangarg/zulip,zulip/zulip,hackerkid/zulip,eeshangarg/zulip,showell/zulip,timabbott/zulip,andersk/zulip,zulip/zulip,dhcrzf/zulip,timabbott/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,tommyip/zulip,dhcrzf/zulip,rishig/zulip,showell/zulip,jackrzhang/zulip,timabbott/zulip,punchagan/zulip,hackerkid/zulip,mahim97/zulip,rishig/zulip,zulip/zulip,shubhamdhama/zulip,timabbott/zulip,punchagan/zulip,hackerkid/zulip,showell/zulip,synicalsyntax/zulip,kou/zulip,rht/zulip