fix(ajustes): group eyebrow outside the card, per-row accent icons

Audit 10.2 (t4:511): GrupoAjustes's eyebrow now sits OUTSIDE the
PluriGlassSurface, at title-tier (20px) padding -- it used to share
the card's own 16px content padding.

Audit 10.5 (t4:514/526): FilaAjuste gains an optional iconColor.
Wired on the two rows the prototype actually accents: AUDIO's
Ecualizador (brand cyan) and STATIONS' Grupos de favoritos (warmCoral).

Item 10.10 (two extra AUDIO rows -- "Calidad de streaming" and
"Reproduccion sin interrupciones") is NOT implemented: neither concept
has any backing state or service anywhere in this app today. Building
them for real means inventing two new persisted settings, and a
genuine streaming-quality preference would plausibly need to touch
the protected servicio_audio.dart to actually affect playback --
out of scope for a visual-fidelity pass. Decorative rows that open
nothing would be dead UI, which is worse than leaving the gap
disclosed.

lib/pantallas/pantalla_ajustes.dart

@@ -9,6 +9,7 @@ import '../l10n/display_names.dart';
 import '../l10n/gen/app_localizations.dart';
 import '../modelos/archivo_grabacion.dart';
 import '../modelos/emisora.dart';
+import '../tema/pluriwave_tokens.dart';
 import '../widgets/pluri_layout.dart';
 import '../widgets/pluri_push_scaffold.dart';
 import '../widgets/pluri_root_header.dart';
@@ -106,6 +107,9 @@ class _AjustesContent extends StatelessWidget {
           filas: [
             FilaAjuste(
               icon: Icons.equalizer_rounded,
+              // Audit 10.5 (t4 line 514): the first AUDIO row's icon is
+              // brand cyan.
+              iconColor: PluriWaveTokens.brand,
               titulo: l10n.equalizerTitle,
               valor:
                   ecualizadorActivo
@@ -149,6 +153,9 @@ class _AjustesContent extends StatelessWidget {
           filas: [
             FilaAjuste(
               icon: Icons.playlist_add_check_circle_rounded,
+              // Audit 10.5 (t4 line 526): the first STATIONS row's icon
+              // is warmCoral (the prototype's own `folder` row accent).
+              iconColor: PluriWaveTokens.dark.warmCoral,
               titulo: l10n.favoriteGroupsTitle,
               valor: '$gruposCount',
               onTap: