feat(organisation): add dashboard-stats endpoint

GET /organisations/{organisation}/dashboard-stats returns members,
events (with status breakdown + active count), persons, the first five
members sorted by join date, and the five most recent activity log
entries. Business logic lives in OrganisationDashboardService; access
follows OrganisationPolicy@view.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Http/Controllers/Api/V1/OrganisationController.php

@@ -7,14 +7,20 @@ namespace App\Http\Controllers\Api\V1;
 use App\Http\Controllers\Controller;
 use App\Http\Requests\Api\V1\StoreOrganisationRequest;
 use App\Http\Requests\Api\V1\UpdateOrganisationRequest;
+use App\Http\Resources\Api\V1\OrganisationDashboardStatsResource;
 use App\Http\Resources\Api\V1\OrganisationResource;
 use App\Models\Organisation;
+use App\Services\OrganisationDashboardService;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Resources\Json\AnonymousResourceCollection;
 use Illuminate\Support\Facades\Gate;
 
 final class OrganisationController extends Controller
 {
+    public function __construct(
+        private readonly OrganisationDashboardService $dashboardService,
+    ) {}
+
     public function index(): AnonymousResourceCollection
     {
         Gate::authorize('viewAny', Organisation::class);
@@ -54,4 +60,13 @@ final class OrganisationController extends Controller
 
         return $this->success(new OrganisationResource($organisation->fresh()));
     }
+
+    public function dashboardStats(Organisation $organisation): JsonResponse
+    {
+        Gate::authorize('view', $organisation);
+
+        return $this->success(new OrganisationDashboardStatsResource(
+            $this->dashboardService->statsFor($organisation),
+        ));
+    }
 }