feat(helpdesk): Übergabe assignment workflow

- New statuses: under_review
- New DB fields: assigned_to, assigned_by, assigned_at, due_date (migration 012)
- HandoverNotificationService: emails on assign and review-request
- HandoverService: assign(), submitForReview(), resendNotification()
- Assign page: manager selects employee + due date, resend notification
- Create wizard: manager can assign during creation (step 1)
- Edit page: "Submit for review" button for assignee, assign link for manager
- List page: open/closed tabs, non-managers see only their assigned handovers
- Email templates: handover_assigned + handover_review_requested (de/en)
- i18n keys added for de and en

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

modules/helpdesk/lib/Module/Helpdesk/Service/HandoverService.php

@@ -15,11 +15,14 @@ class HandoverService
     public const STATUS_COMPLETED = 'completed';
     /** @api Used in pages and templates for status checks */
     public const STATUS_ARCHIVED = 'archived';
+    /** @api Submitted by assignee, awaiting manager review */
+    public const STATUS_UNDER_REVIEW = 'under_review';
 
     /** @api Used in validation */
     public const ALL_STATUSES = [
         self::STATUS_DRAFT,
         self::STATUS_IN_PROGRESS,
+        self::STATUS_UNDER_REVIEW,
         self::STATUS_COMPLETED,
         self::STATUS_ARCHIVED,
     ];
@@ -29,12 +32,12 @@ class HandoverService
 
     /**
      * Status transitions allowed per permission level.
-     * create-level: can set draft, in_progress, completed.
-     * manage-level: can set any status.
+     * create-level: draft → in_progress → under_review.
+     * manage-level: any status.
      */
     private const ALLOWED_STATUS_BY_PERMISSION = [
-        self::PERMISSION_CREATE => [self::STATUS_DRAFT, self::STATUS_IN_PROGRESS, self::STATUS_COMPLETED],
-        self::PERMISSION_MANAGE => [self::STATUS_DRAFT, self::STATUS_IN_PROGRESS, self::STATUS_COMPLETED, self::STATUS_ARCHIVED],
+        self::PERMISSION_CREATE => [self::STATUS_DRAFT, self::STATUS_IN_PROGRESS, self::STATUS_UNDER_REVIEW],
+        self::PERMISSION_MANAGE => [self::STATUS_DRAFT, self::STATUS_IN_PROGRESS, self::STATUS_UNDER_REVIEW, self::STATUS_COMPLETED, self::STATUS_ARCHIVED],
     ];
 
     /**
@@ -46,6 +49,7 @@ class HandoverService
         private readonly HandoverRepository $repository,
         private readonly SoftwareProductService $softwareProductService,
         private readonly ?HandoverRevisionService $revisionService = null,
+        private readonly ?HandoverNotificationService $notificationService = null,
     ) {
     }
 
@@ -258,6 +262,120 @@ class HandoverService
         );
     }
 
+    /**
+     * Assign a handover to a user and optionally set a due date.
+     * Sends notification email to the assignee.
+     *
+     * @return array{ok: bool, errors: array<string, string>}
+     */
+    public function assign(
+        int $tenantId,
+        int $id,
+        int $assignedTo,
+        int $assignedBy,
+        ?string $dueDate,
+        string $permissionLevel,
+    ): array {
+        if ($permissionLevel !== self::PERMISSION_MANAGE) {
+            return ['ok' => false, 'errors' => ['general' => t('Only managers can assign handovers')]];
+        }
+
+        $handover = $this->repository->findById($tenantId, $id);
+        if ($handover === null) {
+            return ['ok' => false, 'errors' => ['general' => t('Handover not found')]];
+        }
+
+        if ($assignedTo <= 0) {
+            return ['ok' => false, 'errors' => ['assigned_to' => t('Please select an employee')]];
+        }
+
+        $updated = $this->repository->assign($tenantId, $id, $assignedTo, $assignedBy, $dueDate, $assignedBy);
+        if (!$updated) {
+            return ['ok' => false, 'errors' => ['general' => t('Failed to assign handover')]];
+        }
+
+        // Transition to in_progress if still draft
+        if ($handover['status'] === self::STATUS_DRAFT) {
+            $this->repository->updateStatus($tenantId, $id, self::STATUS_IN_PROGRESS, $assignedBy);
+        }
+
+        $updatedHandover = $this->repository->findById($tenantId, $id);
+        $this->notificationService?->notifyAssigned($updatedHandover ?? $handover);
+
+        return ['ok' => true, 'errors' => []];
+    }
+
+    /**
+     * Submit handover for review (assignee action).
+     * Changes status to under_review and notifies managers.
+     *
+     * @return array{ok: bool, errors: array<string, string>}
+     */
+    public function submitForReview(
+        int $tenantId,
+        int $id,
+        int $userId,
+        string $permissionLevel,
+    ): array {
+        $handover = $this->repository->findById($tenantId, $id);
+        if ($handover === null) {
+            return ['ok' => false, 'errors' => ['general' => t('Handover not found')]];
+        }
+
+        // Only the assignee or a manager may submit for review
+        $assignedTo = (int) ($handover['assigned_to'] ?? 0);
+        $isAssignee = $assignedTo === $userId;
+        $isManager = $permissionLevel === self::PERMISSION_MANAGE;
+
+        if (!$isAssignee && !$isManager) {
+            return ['ok' => false, 'errors' => ['general' => t('You are not assigned to this handover')]];
+        }
+
+        $currentStatus = (string) ($handover['status'] ?? '');
+        if (!in_array($currentStatus, [self::STATUS_DRAFT, self::STATUS_IN_PROGRESS], true)) {
+            return ['ok' => false, 'errors' => ['status' => t('Handover cannot be submitted for review in its current status')]];
+        }
+
+        $updated = $this->repository->updateStatus($tenantId, $id, self::STATUS_UNDER_REVIEW, $userId);
+        if (!$updated) {
+            return ['ok' => false, 'errors' => ['general' => t('Failed to update status')]];
+        }
+
+        $this->revisionService?->createRevision(
+            $tenantId, $id, [], self::STATUS_UNDER_REVIEW, 1, $userId, HandoverRevisionService::CHANGE_TYPE_STATUS
+        );
+
+        $updatedHandover = $this->repository->findById($tenantId, $id);
+        $this->notificationService?->notifyReviewRequested($updatedHandover ?? $handover);
+
+        return ['ok' => true, 'errors' => []];
+    }
+
+    /**
+     * Resend assignment notification email.
+     *
+     * @return array{ok: bool, errors: array<string, string>}
+     */
+    public function resendNotification(int $tenantId, int $id, string $permissionLevel): array
+    {
+        if ($permissionLevel !== self::PERMISSION_MANAGE) {
+            return ['ok' => false, 'errors' => ['general' => t('Only managers can resend notifications')]];
+        }
+
+        $handover = $this->repository->findById($tenantId, $id);
+        if ($handover === null) {
+            return ['ok' => false, 'errors' => ['general' => t('Handover not found')]];
+        }
+
+        if (empty($handover['assigned_to'])) {
+            return ['ok' => false, 'errors' => ['general' => t('Handover has no assignee')]];
+        }
+
+        $this->notificationService?->notifyAssigned($handover);
+
+        return ['ok' => true, 'errors' => []];
+    }
+
     /**
      * @return array{total: int, rows: list<array<string, mixed>>}
      */
@@ -364,6 +482,7 @@ class HandoverService
         return match ($status) {
             self::STATUS_DRAFT => t('Draft'),
             self::STATUS_IN_PROGRESS => t('In progress'),
+            self::STATUS_UNDER_REVIEW => t('Under review'),
             self::STATUS_COMPLETED => t('Completed'),
             self::STATUS_ARCHIVED => t('Archived'),
             default => $status,
@@ -378,6 +497,7 @@ class HandoverService
         return match ($status) {
             self::STATUS_DRAFT => 'neutral',
             self::STATUS_IN_PROGRESS => 'warning',
+            self::STATUS_UNDER_REVIEW => 'info',
             self::STATUS_COMPLETED => 'success',
             self::STATUS_ARCHIVED => 'neutral',
             default => 'neutral',