fix: compare service days as dates, not raw strings

DateTime.toString() renders "2026-07-13 00:00:00.000Z" while the backend
sends "2026-07-13T00:00:00.000Z", so every day comparison was false and no
booked slot was ever detected. Both calendars showed fully free days.

The client calendar now also treats an unloaded agenda as busy instead of
free: rendering a taken slot as available leads straight to a double booking.

Note: the client still reads /services/professional/calendar, which returns
the *caller's* calendar. There is no endpoint for another professional's
agenda, so a client cannot yet see which of that professional's slots are
taken. That needs a backend endpoint.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

lib/screens/professional/professional_calendar_screen.dart

@@ -6,6 +6,7 @@ import 'package:intl/intl.dart';
 import 'package:professional_repository/professional_repository.dart';
 import 'package:prosappco/blocs/service_bloc/service_bloc.dart';
 import 'package:prosappco/screens/service/professional_service_screen.dart';
+import 'package:prosappco/utils/service_day.dart';
 import 'package:prosappco/utils/time_of_day_extension.dart';
 import 'package:prosappco/utils/time_of_day_utils.dart';
 import 'package:service_repository/service_repository.dart';
@@ -596,7 +597,7 @@ class _ProfessionalCalendarScreenState
       TimeOfDay time, List<ServiceEntity>? services, DateTime day) {
     if (services == null) return null;
     for (final s in services) {
-      if (day.toString() != s.day || s.range1Hour1 != time) continue;
+      if (!isSameServiceDay(day, s.day) || s.range1Hour1 != time) continue;
       if (s.status == ServiceStatus.cancelled ||
           s.status == ServiceStatus.denied) {
         continue;

lib/screens/user/user_calendar_screen.dart

@@ -5,6 +5,7 @@ import 'package:intl/intl.dart';
 import 'package:professional_repository/professional_repository.dart';
 import 'package:prosappco/blocs/professional_list_bloc/professional_list_bloc.dart';
 import 'package:prosappco/utils/time_of_day_extension.dart';
+import 'package:prosappco/utils/service_day.dart';
 import 'package:prosappco/utils/time_of_day_utils.dart';
 import 'package:service_repository/service_repository.dart';
 import 'package:setting_repository/setting_repository.dart';
@@ -233,14 +234,16 @@ class UserCalendarScreenState extends State<UserCalendarScreen> {
 
   bool _isHora1Ocupada(
       TimeOfDay hora1, List<ServiceEntity>? events, DateTime selectedDay) {
-    if (events != null) {
+    // Treat "could not load the agenda" as busy rather than free: showing a
-      for (ServiceEntity event in events) {
+    // taken slot as available leads straight to a double booking.
-        if (selectedDay.toString() == event.day) {
+    if (events == null) return true;
-          if (hora1 == event.range1Hour1) {
+    for (final event in events) {
-            return true;
+      if (!isSameServiceDay(selectedDay, event.day)) continue;
-          }
+      if (event.status == ServiceStatus.cancelled ||
-        }
+          event.status == ServiceStatus.denied) {
+        continue;
       }
+      if (hora1 == event.range1Hour1) return true;
     }
     return false;
   }

lib/utils/service_day.dart

@@ -0,0 +1,14 @@
+/// Whether a service's `day` field refers to the same calendar day as [day].
+///
+/// The backend returns ISO 8601 ("2026-07-13T00:00:00.000Z") while
+/// `DateTime.toString()` produces a space separator ("2026-07-13 00:00:00.000Z"),
+/// so comparing the two as raw strings never matched and every booked slot
+/// rendered as free. Compare parsed calendar dates instead.
+bool isSameServiceDay(DateTime day, String? serviceDay) {
+  if (serviceDay == null || serviceDay.isEmpty) return false;
+  final parsed = DateTime.tryParse(serviceDay);
+  if (parsed == null) return false;
+  return parsed.year == day.year &&
+      parsed.month == day.month &&
+      parsed.day == day.day;
+}