feat: add active section highlight to settings nav for dark themes

Add explicit CSS rules for the active settings navigation button in Metro Teal
and Neon Love themes. The active state background and text colors now match
each theme's color palette (teal for Metro Teal, cyan for Neon Love), making
the currently selected section visually distinct in the settings navigation.

Author: pythoninthegrass

app/frontend/styles.css

@@ -334,6 +334,11 @@ aside button:hover svg {
   border-color: rgba(0, 183, 195, 0.4) !important;
 }
 
+[data-theme-preset='metro-teal'] [data-testid='settings-view'] nav button.bg-primary\/15 {
+  background-color: rgba(0, 183, 195, 0.15) !important;
+  color: #00C4CC !important;
+}
+
 /* Metro-teal scrobbling toggle needs explicit colors (Tailwind bg-primary/bg-muted resolve transparent) */
 [data-theme-preset='metro-teal'] [data-testid='lastfm-toggle'].bg-muted {
   background-color: hsl(0 0% 25%) !important;
@@ -487,6 +492,11 @@ aside button:hover svg {
   border-color: rgba(65, 200, 229, 0.4) !important;
 }
 
+[data-theme-preset='neon-love'] [data-testid='settings-view'] nav button.bg-primary\/15 {
+  background-color: rgba(65, 200, 229, 0.15) !important;
+  color: #41C8E5 !important;
+}
+
 [data-theme-preset='neon-love'] [data-testid='lastfm-toggle'].bg-muted {
   background-color: hsl(268 30% 25%) !important;
 }