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/views/profile_view.dart

@@ -250,6 +250,27 @@ class _ProfileViewForm extends StatelessWidget {
   }
 }
 
+Widget _buildInitials(String name) {
+  final parts = name.trim().split(RegExp(r'\s+'));
+  final initials = parts.length >= 2
+      ? '${parts.first[0]}${parts.last[0]}'.toUpperCase()
+      : (parts.first.isEmpty ? '?' : parts.first[0].toUpperCase());
+  final colors = [
+    const Color(0xFF6366F1), const Color(0xFF8B5CF6),
+    const Color(0xFFEC4899), const Color(0xFF14B8A6),
+    const Color(0xFFF59E0B), const Color(0xFF10B981),
+    const Color(0xFFEF4444), const Color(0xFF3B82F6),
+  ];
+  final bg = name.isEmpty ? colors[0] : colors[name.codeUnitAt(0) % colors.length];
+  return Container(
+    color: bg,
+    child: Center(
+      child: Text(initials,
+          style: const TextStyle(color: Colors.white, fontSize: 48, fontWeight: FontWeight.bold)),
+    ),
+  );
+}
+
 class _AvatarContainer extends StatelessWidget {
   final bool containerFull;
 
@@ -260,14 +281,18 @@ class _AvatarContainer extends StatelessWidget {
     final user = Provider.of<AuthProvider>(context).user!;
     final profileFormProvider = Provider.of<ProfileFormProvider>(context);
 
-    final image = (profileFormProvider.user!.picture == '' ||
-            profileFormProvider.user!.picture == null)
-        ? const Image(image: AssetImage('no-image.jpg'))
-        : FadeInImage.assetNetwork(
-            placeholder: 'loader.gif',
-            fit: BoxFit.cover,
-            image: profileFormProvider.user!.picture!,
-          );
+    final picUrl = profileFormProvider.user!.picture;
+    final hasPicture = picUrl != null && picUrl.isNotEmpty;
+    final userName = profileFormProvider.user!.name;
+
+    Widget avatarImage;
+    if (hasPicture) {
+      avatarImage = Image.network(picUrl, fit: BoxFit.cover,
+          errorBuilder: (_, __, ___) => _buildInitials(userName));
+    } else {
+      avatarImage = _buildInitials(userName);
+    }
+    final image = avatarImage;
 
     return WhiteCard(
       width: containerFull ? null : 250,