Add test utilities and state machine diagrams for FSM models

- Introduced reusable test utilities in `backend/tests/utils` for FSM transitions, HTMX interactions, and common scenarios.
- Added factory functions for creating test submissions, parks, rides, and photo submissions.
- Implemented assertion helpers for verifying state changes, toast notifications, and transition logs.
- Created comprehensive state machine diagrams for all FSM-enabled models in `docs/STATE_DIAGRAMS.md`, detailing states, transitions, and guard conditions.

backend/apps/parks/urls.py

@@ -1,6 +1,7 @@
 from django.urls import path, include
 from . import views, views_search
 from apps.rides.views import ParkSingleCategoryListView
+from apps.core.views.views import FSMTransitionView
 from .views_roadtrip import (
     RoadTripPlannerView,
     CreateTripView,
@@ -99,6 +100,8 @@ urlpatterns = [
     path("<slug:slug>/", views.ParkDetailView.as_view(), name="park_detail"),
     path("<slug:slug>/edit/", views.ParkUpdateView.as_view(), name="park_update"),
     path("<slug:slug>/actions/", views.park_actions, name="park_actions"),
+    path("<slug:slug>/status-actions/", views.park_status_actions, name="park_status_actions"),
+    path("<slug:slug>/header-badge/", views.park_header_badge, name="park_header_badge"),
     # Area views
     path(
         "<slug:park_slug>/areas/<slug:area_slug>/",
@@ -147,4 +150,12 @@ urlpatterns = [
         "<slug:park_slug>/rides/",
         include("apps.rides.park_urls", namespace="rides"),
     ),
+    # FSM transition endpoint for parks
+    # URL: /parks/<slug>/transition/<transition_name>/
+    path(
+        "<slug:slug>/transition/<str:transition_name>/",
+        FSMTransitionView.as_view(),
+        {"app_label": "parks", "model_name": "park"},
+        name="park_transition",
+    ),
 ]

backend/apps/parks/views.py

@@ -132,6 +132,29 @@ def park_actions(request: HttpRequest, slug: str) -> HttpResponse:
     return render(request, "parks/partials/park_actions.html", {"park": park})
 
 
+def park_status_actions(request: HttpRequest, slug: str) -> HttpResponse:
+    """Return FSM status actions for park moderators"""
+    park = get_object_or_404(Park, slug=slug)
+
+    # Only show to moderators
+    if not request.user.has_perm('parks.change_park'):
+        return HttpResponse("")
+
+    return render(request, "parks/partials/park_status_actions.html", {
+        "park": park,
+        "user": request.user
+    })
+
+
+def park_header_badge(request: HttpRequest, slug: str) -> HttpResponse:
+    """Return the header status badge partial for a park"""
+    park = get_object_or_404(Park, slug=slug)
+    return render(request, "parks/partials/park_header_badge.html", {
+        "park": park,
+        "user": request.user
+    })
+
+
 def get_park_areas(request: HttpRequest) -> HttpResponse:
     """Return park areas as options for a select element"""
     park_id = request.GET.get("park")