feat: dodaj bilješke widget i admin kalendar/notifikacije

Uveden je novi Notes drawer s kalendar integracijom, zajednički DRY
left-slide mehanizam te međusobno isključivo prikazivanje s Kalendar
widgetom.

Backend i frontend su prošireni za servisne bilješke (uključujući slanje
na više servisera), dodan je users/servicers endpoint, te su uvedene
warning notifikacije kada serviser ima više od 2 zadatka isti dan.

U admin su dodane stavke za Bilješke i zaseban Kalendar zadataka (proxy
TaskCalendar) radi lakšeg operativnog pregleda.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/modules/task_management/services.py

@@ -1,8 +1,9 @@
 # backend/modules/task_management/services.py
 
-from django.db import transaction
+from django.db import transaction, models
 from rest_framework.exceptions import ValidationError
 from django.core.exceptions import ValidationError as DjangoValidationError
+from django.contrib.auth import get_user_model
 import logging
 
 from .models import Task, TaskTemplate, TaskWorkEntry
@@ -10,6 +11,21 @@ from .exceptions import OpenWorkOrderBlockingTaskClose
 from modules.fleet.models import VehicleServiceRecord
 
 logger = logging.getLogger(__name__)
+User = get_user_model()
+
+
+def _task_overload_recipients(task):
+    recipients = []
+    if task.assigned_to_id:
+        recipients.append(task.assigned_to)
+    supervisors = User.objects.filter(is_active=True).filter(
+        models.Q(is_staff=True) | (models.Q(is_team_member=True) & models.Q(is_serviser=False))
+    )
+    recipients.extend(supervisors)
+    unique = {}
+    for recipient in recipients:
+        unique[str(recipient.id)] = recipient
+    return list(unique.values())
 
 
 class TaskService:
@@ -53,6 +69,7 @@ class TaskService:
 
         with transaction.atomic():
             entry.save()
+            TaskService._notify_if_servicer_overloaded(entry)
             if template:
                 TaskService._create_work_entries_from_template(task=entry, template=template)
                 TaskService._create_service_records_from_template(task=entry, template=template, user=user)
@@ -60,6 +77,49 @@ class TaskService:
         logger.info(f"Zadatak uspješno kreiran: {entry.id}")
         return entry
 
+    @staticmethod
+    def _notify_if_servicer_overloaded(entry: Task):
+        if not entry.assigned_to_id or not entry.scheduled_date:
+            return
+        if not getattr(entry.assigned_to, 'is_serviser', False):
+            return
+
+        task_count = Task.objects.filter(
+            is_active=True,
+            assigned_to=entry.assigned_to,
+            scheduled_date=entry.scheduled_date,
+            status__in=('aktivan', 'servis', 'spreman_za_zavrsetak'),
+        ).count()
+        if task_count <= 2:
+            return
+
+        from modules.fleet.services import NotificationService
+
+        schedule_label = entry.scheduled_date.strftime('%d.%m.%Y')
+        title = f"Preopterećenje rasporeda: {entry.assigned_to.get_full_name() or entry.assigned_to.email}"
+        message = (
+            f"Serviseru {entry.assigned_to.get_full_name() or entry.assigned_to.email} "
+            f"je dodijeljeno {task_count} zadatka za {schedule_label}. "
+            f"Sustav je dopustio i dodatni zadatak."
+        )
+        metadata = {
+            "entity_type": "task_overload",
+            "assigned_to_id": str(entry.assigned_to_id),
+            "task_id": str(entry.id),
+            "scheduled_date": entry.scheduled_date.isoformat(),
+            "task_count": task_count,
+            "section": "dashboard",
+        }
+        for recipient in _task_overload_recipients(entry):
+            NotificationService.create_notification(
+                recipient=recipient,
+                title=title,
+                message=message,
+                level='warning',
+                send_email=False,
+                metadata=metadata,
+            )
+
     @staticmethod
     def _create_work_entries_from_template(*, task: Task, template: TaskTemplate):
         template_entries = list(template.entries.filter(is_active=True).order_by('sort_order', 'created_at')[:10])