fix(scheduling): fix schedule save endpoint, time format, and calendar load

Critical fixes for the scheduling flow:

- ScheduleEntity: add toScheduleDto() with snake_case keys, day_of_week,
  and HH:MM zero-padded format required by the backend DTO @Matches validator
- Schedules: add toSchedulesArray() converting the day-keyed object to the
  array format expected by PATCH /professionals/me/schedules
- ProfessionalFormProvider: updateProfesionalProfileScheduleInfo now calls
  the correct endpoint (/professionals/me/schedules) instead of /professionals/me
  which was stripping the schedules field via ValidationPipe whitelist
- Service.formatTimeOfDay: zero-pad hours and minutes so POST /services passes
  the @Matches(/^\d{2}:\d{2}$/) DTO validation
- ProfessionalProvider: add getProfessionalById() calling /professionals/:id
  (public endpoint) to load any professional's data, not the viewer's own
- CalendarServicesProvider: add getPublicServicesForProfessional() calling
  /services/public-calendar/:id so the user calendar shows the target
  professional's booked slots, not the viewer's own services
- CalendarView: use getProfessionalById + getPublicServicesForProfessional
  so the calendar correctly reflects the selected professional's schedule

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

lib/models/schedules.dart

@@ -73,4 +73,18 @@ class Schedules {
       'sunday': sunday.toJson(),
     };
   }
+
+  // Produces the array format expected by PATCH /professionals/me/schedules
+  // day_of_week: 0=Monday … 6=Sunday (matches backend DB convention)
+  List<Map<String, dynamic>> toSchedulesArray() {
+    return [
+      monday.toScheduleDto(0),
+      tuesday.toScheduleDto(1),
+      wednesday.toScheduleDto(2),
+      thursday.toScheduleDto(3),
+      friday.toScheduleDto(4),
+      saturday.toScheduleDto(5),
+      sunday.toScheduleDto(6),
+    ];
+  }
 }