feat(backend): Aufgaben-Modul (Modul 6)

TasksModule mit CRUD, Status-/Prioritätsfilter und
Erledigen-Endpunkt für polymorph verknüpfte Aufgaben.

ApiCore-Backend/src/tasks/tasks.service.ts

@@ -0,0 +1,93 @@
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+import { Task, TaskPriority, TaskStatus } from '../../generated/prisma';
+import { CreateTaskDto } from './dto/create-task.dto';
+import { UpdateTaskDto } from './dto/update-task.dto';
+
+export interface TaskFilter {
+  status?: TaskStatus;
+  priority?: TaskPriority;
+}
+
+@Injectable()
+export class TasksService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly auditLog: AuditLogService,
+  ) {}
+
+  async findAll(filter: TaskFilter): Promise<Task[]> {
+    return this.prisma.task.findMany({
+      where: filter,
+      orderBy: [{ dueDate: 'asc' }, { createdAt: 'desc' }],
+    });
+  }
+
+  async findById(id: string): Promise<Task> {
+    const task = await this.prisma.task.findUnique({ where: { id } });
+    if (!task) {
+      throw new NotFoundException('Task not found');
+    }
+    return task;
+  }
+
+  async create(dto: CreateTaskDto, actingUserId: string): Promise<Task> {
+    const task = await this.prisma.task.create({
+      data: {
+        ...dto,
+        dueDate: dto.dueDate ? new Date(dto.dueDate) : undefined,
+        createdByUserId: actingUserId,
+      },
+    });
+    await this.auditLog.record({
+      entityType: 'Task',
+      entityId: task.id,
+      action: 'CREATE',
+      userId: actingUserId,
+      afterData: task,
+    });
+    return task;
+  }
+
+  async update(
+    id: string,
+    dto: UpdateTaskDto,
+    actingUserId: string,
+  ): Promise<Task> {
+    const before = await this.findById(id);
+    const task = await this.prisma.task.update({
+      where: { id },
+      data: {
+        ...dto,
+        dueDate: dto.dueDate ? new Date(dto.dueDate) : undefined,
+      },
+    });
+    await this.auditLog.record({
+      entityType: 'Task',
+      entityId: id,
+      action: 'UPDATE',
+      userId: actingUserId,
+      beforeData: before,
+      afterData: task,
+    });
+    return task;
+  }
+
+  async complete(id: string, actingUserId: string): Promise<Task> {
+    const before = await this.findById(id);
+    const task = await this.prisma.task.update({
+      where: { id },
+      data: { status: 'DONE', completedAt: new Date() },
+    });
+    await this.auditLog.record({
+      entityType: 'Task',
+      entityId: id,
+      action: 'UPDATE',
+      userId: actingUserId,
+      beforeData: before,
+      afterData: task,
+    });
+    return task;
+  }
+}