feat(ui): design token discipline, accessibility and i18n pass

- Replace all hardcoded Color literals outside lib/tema with theme tokens (new static brand palette in PluriWaveTokens); media notification uses the brand color instead of the Material default purple
- Favorite button on station cards grows to a 48dp target and becomes an independent semantics node for screen readers (Semantics container fix)
- All flutter_animate call sites route through the PluriAnimate reduced-motion gate (zero direct .animate() left)
- Locale-aware short dates via intl DateFormat (new lib/l10n/formato_fechas.dart) replacing the hardcoded DD/MM/YYYY; proper plural messages for the favorites counter; example stream URL as a localized key - all 13 locales
- Rounded shimmer placeholders matching card radii; shimmer loading state in search instead of a bare spinner; rounded icon variants unified in settings; bottom-sheet conventions on the custom station form
- Fix latent debug crash: vacation editor read AppLocalizations in initState
- 11 new tests (121 total green), flutter analyze clean

lib/widgets/pluri_premium_widgets.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 
 import '../tema/pluriwave_theme.dart';
+import '../tema/pluriwave_tokens.dart';
 import 'pluri_glass_surface.dart';
 import 'pluri_icon.dart';
 
@@ -38,12 +39,14 @@ class PluriScreenHeader extends StatelessWidget {
         shape: BoxShape.circle,
         gradient: LinearGradient(
           colors: [
-            const Color(0xFF20E6FF).withValues(alpha: 0.95),
+            PluriWaveTokens.brightCyan.withValues(alpha: 0.95),
             t.electricMagenta,
             t.warmCoral,
           ],
         ),
-        boxShadow: [BoxShadow(color: t.glowColor, blurRadius: 28, spreadRadius: 2)],
+        boxShadow: [
+          BoxShadow(color: t.glowColor, blurRadius: 28, spreadRadius: 2),
+        ],
       ),
       child: Center(
         child: PluriIcon(
@@ -117,14 +120,22 @@ class PluriScreenHeader extends StatelessWidget {
           Expanded(child: textBlock()),
           if (trailing != null) ...[
             const SizedBox(width: 12),
-            ConstrainedBox(constraints: const BoxConstraints(maxWidth: 220), child: trailing!),
+            ConstrainedBox(
+              constraints: const BoxConstraints(maxWidth: 220),
+              child: trailing!,
+            ),
           ],
         ],
       );
     }
 
     return Padding(
-      padding: EdgeInsets.fromLTRB(t.spacingMd, t.spacingSm, t.spacingMd, t.spacingSm),
+      padding: EdgeInsets.fromLTRB(
+        t.spacingMd,
+        t.spacingSm,
+        t.spacingMd,
+        t.spacingSm,
+      ),
       child: PluriGlassSurface(
         borderRadius: BorderRadius.circular(t.radiusLg + 8),
         padding: EdgeInsets.symmetric(
@@ -164,7 +175,10 @@ class PluriScreenHeader extends StatelessWidget {
             Positioned(
               right: -36,
               top: -42,
-              child: _Orb(color: t.electricMagenta.withValues(alpha: 0.38), size: 128),
+              child: _Orb(
+                color: t.electricMagenta.withValues(alpha: 0.38),
+                size: 128,
+              ),
             ),
             Positioned(
               right: 10,
@@ -182,7 +196,10 @@ class PluriScreenHeader extends StatelessWidget {
             Positioned(
               right: 44,
               bottom: -54,
-              child: _Orb(color: const Color(0xFF20E6FF).withValues(alpha: 0.22), size: 116),
+              child: _Orb(
+                color: PluriWaveTokens.brightCyan.withValues(alpha: 0.22),
+                size: 116,
+              ),
             ),
             Padding(
               padding: EdgeInsets.all(compact ? 2 : 4),
@@ -195,7 +212,6 @@ class PluriScreenHeader extends StatelessWidget {
   }
 }
 
-
 class PluriStatusPill extends StatelessWidget {
   const PluriStatusPill({
     super.key,
@@ -232,7 +248,9 @@ class PluriStatusPill extends StatelessWidget {
                 label,
                 maxLines: 1,
                 overflow: TextOverflow.ellipsis,
-                style: Theme.of(context).textTheme.labelMedium?.copyWith(fontWeight: FontWeight.w800),
+                style: Theme.of(
+                  context,
+                ).textTheme.labelMedium?.copyWith(fontWeight: FontWeight.w800),
               ),
             ),
           ],
@@ -267,14 +285,26 @@ class PluriEmptyState extends StatelessWidget {
           child: Column(
             mainAxisSize: MainAxisSize.min,
             children: [
-              PluriIcon(glyph: glyph, variant: PluriIconVariant.activeGlow, size: 58),
+              PluriIcon(
+                glyph: glyph,
+                variant: PluriIconVariant.activeGlow,
+                size: 58,
+              ),
               const SizedBox(height: 18),
-              Text(title, textAlign: TextAlign.center, style: theme.textTheme.titleLarge?.copyWith(fontWeight: FontWeight.w900)),
+              Text(
+                title,
+                textAlign: TextAlign.center,
+                style: theme.textTheme.titleLarge?.copyWith(
+                  fontWeight: FontWeight.w900,
+                ),
+              ),
               const SizedBox(height: 8),
               Text(
                 subtitle,
                 textAlign: TextAlign.center,
-                style: theme.textTheme.bodyMedium?.copyWith(color: theme.colorScheme.onSurface.withValues(alpha: 0.72)),
+                style: theme.textTheme.bodyMedium?.copyWith(
+                  color: theme.colorScheme.onSurface.withValues(alpha: 0.72),
+                ),
               ),
             ],
           ),