[FIX][UI] UI adjustments including: - Specify navbar height in Basic Bootstrap...

• [FIX][UI] UI adjustments including: - Specify navbar height in Basic Bootstrap layout with prefs.theme_navbar_fixed_topbar_offset in case logo module isn't assigned (which normally controls the navbar height) - Simplify CSS variables related to top navbar borders - In UAB, prevent light navbar and side menu in dark color mode (giving color mode priority over L and F admin navbar color), so same as with global navbars.