feat: send FCM push notification on service status change + update docs

- services.module: import NotificationsModule
- services.service: inject NotificationsService, notify the other party
  (user or professional) when service status changes to accepted/denied/
  cancelled/active/completed
- ARQUITECTURA.md: updated to reflect current migration state (all migrated)

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

backend/src/services/services.module.ts

@@ -2,9 +2,10 @@ import { Module } from '@nestjs/common';
 import { ServicesService } from './services.service';
 import { ServicesController } from './services.controller';
 import { AuthModule } from '../auth/auth.module';
+import { NotificationsModule } from '../notifications/notifications.module';
 
 @Module({
-  imports: [AuthModule],
+  imports: [AuthModule, NotificationsModule],
   providers: [ServicesService],
   controllers: [ServicesController],
   exports: [ServicesService],

backend/src/services/services.service.ts

@@ -1,11 +1,21 @@
 import { Injectable, NotFoundException, BadRequestException, ForbiddenException } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
+import { NotificationsService } from '../notifications/notifications.service';
 import { ServiceStatus, VALID_TRANSITIONS } from './dto/service.dto';
 
+const STATUS_MESSAGES: Partial<Record<ServiceStatus, { title: string; body: string }>> = {
+  [ServiceStatus.ACCEPTED]: { title: 'Servicio aceptado', body: 'El profesional aceptó tu solicitud.' },
+  [ServiceStatus.DENIED]:   { title: 'Servicio rechazado', body: 'El profesional rechazó tu solicitud.' },
+  [ServiceStatus.CANCELLED]:{ title: 'Servicio cancelado', body: 'El servicio fue cancelado.' },
+  [ServiceStatus.ACTIVE]:   { title: 'Servicio iniciado', body: 'El profesional inició el servicio.' },
+  [ServiceStatus.COMPLETED]:{ title: 'Servicio completado', body: '¡El servicio ha finalizado! Puedes dejar tu puntuación.' },
+};
+
 @Injectable()
 export class ServicesService {
   constructor(
     private prisma: PrismaService,
+    private notifications: NotificationsService,
   ) {}
 
   async create(data: {
@@ -74,10 +84,26 @@ export class ServicesService {
       }
     }
 
-    return this.prisma.services.update({
+    const updated = await this.prisma.services.update({
       where: { id: serviceId },
       data: { status: newStatus as any },
     });
+
+    // Notify the other party
+    const msg = STATUS_MESSAGES[newStatus];
+    if (msg) {
+      const targetUserId = userId === service.user_id
+        ? (await this.prisma.professionals.findUnique({ where: { id: service.professional_id } }))?.user_id
+        : service.user_id;
+      if (targetUserId) {
+        const target = await this.prisma.users.findUnique({ where: { id: targetUserId }, select: { fcm_token: true } });
+        if (target?.fcm_token) {
+          this.notifications.send(target.fcm_token, msg.title, msg.body).catch(() => {});
+        }
+      }
+    }
+
+    return updated;
   }
 
   async findByUser(userId: string, page = 1, limit = 20) {