AG-21136 - Added local storage theme key.

Updates#5444

Squashed commit of the following:

commit 7b0b108f41ebb5e98861cdd20029c12d3a3fc5f4
Merge: 38df28db0 e43ba1788
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Mon Apr 17 15:58:15 2023 +0300

    Merge branch 'master' of ssh://bit.adguard.com:7999/dns/adguard-home into 5444-white-screen

commit 38df28db0739e47d3fb605f648fa493b58709d77
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Fri Apr 14 17:54:00 2023 +0300

    Deleted useless tag.

commit 78ef9d911ccf74b69a9ae5626ea8f31cb9338ae0
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Fri Apr 14 17:53:17 2023 +0300

    Set initial body data-theme.

commit f470b3aa79500edd0726b7ed37e6e5940b6ce3ff
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Thu Apr 13 16:42:25 2023 +0300

    Revert login changes.

commit 7c4734ed02a670a59d0b9ff04e06bc1d396223a8
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Thu Apr 13 15:51:24 2023 +0300

    Added setting theme into html.Changed overlay background color to variable.

commit a3743be0e69489489755db8ff55541b9a6281300
Author: Artem Krisanov <a.krisanov@adguard.com>
Date:   Wed Apr 12 17:58:47 2023 +0300

    Added local storage theme key.

client/src/components/ui/Footer.js

@@ -1,4 +1,4 @@
-import React, { useState, useEffect } from 'react';
+import React, { useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useDispatch, useSelector } from 'react-redux';
 import cn from 'classnames';
@@ -42,12 +42,6 @@ const Footer = () => {
     const isLoggedIn = profileName !== '';
     const [currentThemeLocal, setCurrentThemeLocal] = useState(THEMES.auto);
 
-    useEffect(() => {
-        if (!isLoggedIn) {
-            setUITheme(currentThemeLocal);
-        }
-    }, []);
-
     const getYear = () => {
         const today = new Date();
         return today.getFullYear();

client/src/components/ui/Overlay.css

@@ -13,7 +13,7 @@
     font-size: 28px;
     font-weight: 600;
     text-align: center;
-    background-color: rgba(255, 255, 255, 0.8);
+    background-color: var(--rt-nodata-bgcolor);
 }
 
 .overlay--visible {