feat: pedir nombre al primer login + avatar con iniciales

- Detectar usuario nuevo (nombre == telefono) y redirigir
  a pantalla setup-name antes del dashboard
- SetupNameView: bienvenida con campo de nombre obligatorio
- AuthProvider.updateName() para guardar via PATCH /users/me
- NavbarAvatar: iniciales con color por inicial del nombre
  en lugar de no-image.jpg cuando no hay foto
- Perfil: mismo avatar de iniciales en la pantalla de perfil

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

lib/ui/shared/widgets/navbar_avatar.dart

@@ -10,23 +10,68 @@ class NavbarAvatar extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final user = Provider.of<AuthProvider>(context).user!;
-
-    final image = (user.picture == '' || user.picture == null)
-        ? const Image(image: AssetImage('no-image.jpg'))
-        : FadeInImage.assetNetwork(
-            placeholder: 'loader.gif',
-            fit: BoxFit.cover,
-            image: user.picture!,
-          );
+    final hasPicture = user.picture != null && user.picture!.isNotEmpty;
 
     return MouseRegion(
       cursor: SystemMouseCursors.click,
       child: GestureDetector(
         onTap: () => NavigationService.replaceTo(Flurorouter.profileRoute),
         child: SizedBox(
-          width: 40,
-          height: 40,
-          child: ClipOval(child: image),
+          width: 36,
+          height: 36,
+          child: ClipOval(
+            child: hasPicture
+                ? Image.network(
+                    user.picture!,
+                    fit: BoxFit.cover,
+                    errorBuilder: (_, __, ___) => _InitialsAvatar(name: user.name),
+                  )
+                : _InitialsAvatar(name: user.name),
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class _InitialsAvatar extends StatelessWidget {
+  final String name;
+  const _InitialsAvatar({required this.name});
+
+  String get _initials {
+    final parts = name.trim().split(RegExp(r'\s+'));
+    if (parts.isEmpty || parts.first.isEmpty) return '?';
+    if (parts.length == 1) return parts.first[0].toUpperCase();
+    return (parts.first[0] + parts.last[0]).toUpperCase();
+  }
+
+  Color get _bgColor {
+    final colors = [
+      const Color(0xFF6366F1), // indigo
+      const Color(0xFF8B5CF6), // violet
+      const Color(0xFFEC4899), // pink
+      const Color(0xFF14B8A6), // teal
+      const Color(0xFFF59E0B), // amber
+      const Color(0xFF10B981), // emerald
+      const Color(0xFFEF4444), // red
+      const Color(0xFF3B82F6), // blue
+    ];
+    final index = name.isEmpty ? 0 : name.codeUnitAt(0) % colors.length;
+    return colors[index];
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      color: _bgColor,
+      child: Center(
+        child: Text(
+          _initials,
+          style: const TextStyle(
+            color: Colors.white,
+            fontSize: 13,
+            fontWeight: FontWeight.bold,
+          ),
         ),
       ),
     );