Refactor email system and add contact form backend

Refactored email sending to use a single HTML template with a base layout, removed plain text email templates, and updated all related backend logic. Introduced a new ContactMe model, serializer, Celery task, and API endpoints for handling contact form submissions, including email notifications. Renamed ShopConfiguration to SiteConfiguration throughout the backend for consistency. Updated frontend to remove unused components, add a new Services section, and adjust navigation and contact form integration.

backend/thirdparty/zasilkovna/views.py

@@ -5,7 +5,7 @@ from django.template import loader
 
 from drf_spectacular.utils import extend_schema, extend_schema_view, OpenApiResponse, OpenApiParameter, OpenApiTypes
 
-from backend.configuration.models import ShopConfiguration
+from backend.configuration.models import SiteConfiguration
 
 from .models import ZasilkovnaShipment, ZasilkovnaPacket
 from .serializers import (
@@ -135,7 +135,7 @@ class ZasilkovnaPacketViewSet(mixins.RetrieveModelMixin, viewsets.GenericViewSet
         widget_html = loader.render_to_string(
             "zasilkovna/pickup_point_widget.html",
             {
-                "api_key": ShopConfiguration.get_solo().zasilkovna_widget_api_key,
+                "api_key": SiteConfiguration.get_solo().zasilkovna_widget_api_key,
             }
         )