[FIX] web: search, adapt mobile search for dark mode

Prior to this commit, the mobile search colors used in dark mode were
incorrect. This commit adapts the mobile search colors for dark mode.

task-3012970

X-original-commit: 5408fadba20a59ce2e186821350b56b2347f7685
Part-of: odoo/odoo#103132

addons/web/static/src/search/search_panel/search_view.scss

@@ -150,7 +150,7 @@
 
 .o_web_client .o_mobile_search {
     align-items: normal;
-    background-color: white;
+    background-color: var(--mobileSearch-bg, #{$o-white});
     border: none;
     bottom: 0;
     display: flex;
@@ -164,7 +164,7 @@
     z-index: $zindex-modal;
 
     .o_mobile_search_header {
-        background-color: $o-brand-odoo;
+        background-color: var(--mobileSearch__header-bg, #{$o-brand-odoo});
         display: flex;
         min-height: $o-navbar-height;
         justify-content: space-between;