fix: 4 audit findings in professionals location flow

- Clear button (✕) now resets _cityMismatch and _detectedCity so banner and CTA unblock
- _citiesMatch: replace bidirectional contains with equality + word-prefix check to prevent 'Cali' matching 'Calima'
- ProfessionalsProvider: track _currentUserId to reset state on user change (cross-user leak)
- ProfessionalsProvider: store _lastSearch so setLocationContext preserves active search term

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

lib/providers/professionals_provider.dart

@@ -6,12 +6,24 @@ class ProfessionalsProvider extends ChangeNotifier {
   List<UsuarioProfesional> professionals = [];
   bool isLoading = true;
   bool _initialized = false;
+  String? _currentUserId;
   String? _locationCity;
   double? _locationLat;
   double? _locationLng;
+  String? _lastSearch;
   final _api = ApiService.instance;
 
-  void updateCity(String? city) {
+  void updateCity(String? city, {String? userId}) {
+    // Reset state when a different user logs in (prevents cross-user data leak)
+    if (_currentUserId != userId) {
+      _currentUserId = userId;
+      _initialized = false;
+      _locationCity = null;
+      _locationLat = null;
+      _locationLng = null;
+      _lastSearch = null;
+      professionals = [];
+    }
     if (!_initialized) {
       _initialized = true;
       _locationCity = city;
@@ -23,15 +35,16 @@ class ProfessionalsProvider extends ChangeNotifier {
     if (city != null && city.isNotEmpty) _locationCity = city;
     _locationLat = lat;
     _locationLng = lng;
-    getProfessionals();
+    getProfessionals(search: _lastSearch);
   }
 
   Future<void> getProfessionals({String? search}) async {
+    if (search != null) _lastSearch = search.trim().isEmpty ? null : search.trim();
     isLoading = true;
     notifyListeners();
     try {
       final params = <String, String>{};
-      if (search != null && search.trim().isNotEmpty) params['search'] = search.trim();
+      if (_lastSearch != null && _lastSearch!.isNotEmpty) params['search'] = _lastSearch!;
       if (_locationCity != null && _locationCity!.isNotEmpty) params['city'] = _locationCity!.trim();
       if (_locationLat != null) params['lat'] = _locationLat.toString();
       if (_locationLng != null) params['lng'] = _locationLng.toString();