Fix dark mode: main settings nav tab buttons showing white UA background

The #settingsTabs <button> elements had no explicit background-color,
letting browser UA button styling (white) bleed through in dark mode.
Added transparent overrides so the dark body background shows instead.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/wwwroot/css/company-settings-lookups.css

@@ -88,6 +88,20 @@
     border-bottom: 3px solid var(--bs-primary);
 }
 
+/* ── Dark mode fix for main settings tabs: UA button styling bleeds through
+   without an explicit background-color, producing white buttons with faint text. */
+[data-bs-theme="dark"] #settingsTabs .nav-link {
+    background-color: transparent;
+}
+
+[data-bs-theme="dark"] #settingsTabs .nav-link:hover:not(.active) {
+    background-color: var(--bs-tertiary-bg);
+}
+
+[data-bs-theme="dark"] #settingsTabs .nav-link.active {
+    background-color: var(--bs-body-bg);
+}
+
 /* ── PDF Templates inner tabs (card-header-tabs) ────────────────────────── */
 #pdfTemplateTabs .nav-link {
     color: var(--bs-secondary-color);