feat(mornye): add persistent accent color choices

lib/widgets/audio_analysis_spectrogram.dart

@@ -147,7 +147,10 @@ class _SpectrogramView extends StatelessWidget {
     // The plot stays black in both appearances; its controls need matching
     // contrast even when the surrounding Mornye page uses the light theme.
     return context.isMornye
-        ? Theme(data: MornyeTheme.build(Brightness.dark), child: card)
+        ? Theme(
+            data: MornyeTheme.fromContext(context, brightness: Brightness.dark),
+            child: card,
+          )
         : card;
   }