feat: SMS OTP auth + phone verification gate + improved login UI

- Usuario model: add isPhoneVerified field from is_phone_verified
- auth_provider.dart: fix access_token key, add _navigateAfterAuth gate
  (redirects to phoneLoginRoute if phone not verified), add verifyPhoneNumber,
  signInWithOTP, verifyPhoneNumberForLink, linkPhoneWithOTP methods
- phone_login_view.dart: full rewrite with logo, +57 prefix, two-step OTP flow
  (phone input → code input), 60s resend timer, email login fallback

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

lib/models/usuario.dart

@@ -12,6 +12,7 @@ class Usuario {
   final String? gender;
   final ProState proState;
   final String? token;
+  final bool isPhoneVerified;
 
   Usuario({
     required this.id,
@@ -25,6 +26,7 @@ class Usuario {
     required this.gender,
     required this.proState,
     required this.token,
+    this.isPhoneVerified = false,
   });
 
   Map<String, Object?> toDocument() {
@@ -56,6 +58,7 @@ class Usuario {
       gender: doc['gender'],
       proState: intToEnum((doc['professional_state'] as int?) ?? 0),
       token: doc['token'],
+      isPhoneVerified: doc['is_phone_verified'] as bool? ?? false,
     );
   }