feature: a minimal implementation of the appointment feature done.

backend/src/modules/appointments/dto/create-appointment.dto.ts

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+import { ApiProperty } from '@nestjs/swagger';
+import { IsDateString, IsIn, IsUUID } from 'class-validator';
+
+const APPOINTMENT_PURPOSES = ['consultation', 'filling', 'endo', 'visit', 'hygiene'] as const;
+
+export type AppointmentPurpose = (typeof APPOINTMENT_PURPOSES)[number];
+
+export class CreateAppointmentDto {
+  @ApiProperty()
+  @IsUUID()
+  patientId: string;
+
+  @ApiProperty({ description: 'Staff user id (column provider)' })
+  @IsUUID()
+  providerUserId: string;
+
+  @ApiProperty({ example: '2026-05-06T09:15:00.000Z' })
+  @IsDateString()
+  startAt: string;
+
+  @ApiProperty({ example: '2026-05-06T09:45:00.000Z' })
+  @IsDateString()
+  endAt: string;
+
+  @ApiProperty({ enum: APPOINTMENT_PURPOSES })
+  @IsIn([...APPOINTMENT_PURPOSES])
+  purpose: AppointmentPurpose;
+}

backend/src/modules/appointments/dto/list-appointments.dto.ts

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+import { ApiProperty } from '@nestjs/swagger';
+import { IsDateString } from 'class-validator';
+
+export class ListAppointmentsDto {
+  @ApiProperty({ description: 'Range start (ISO 8601), e.g. local midnight as instant' })
+  @IsDateString()
+  from: string;
+
+  @ApiProperty({ description: 'Range end (ISO 8601), e.g. next local midnight' })
+  @IsDateString()
+  to: string;
+}