Fix FEniCS import - use lazy loading to avoid import during migrations

backend/poisson/views.py

@@ -4,10 +4,15 @@ from rest_framework.response import Response
 from django.http import JsonResponse
 from .models import PoissonSimulation
 from .serializers import PoissonSimulationSerializer, PoissonSimulationCreateSerializer
-from .solver import solve_poisson, generate_preview_mesh
 import traceback
 
 
+def get_solver():
+    """Lazy import of solver to avoid FEniCS import at module load time"""
+    from .solver import solve_poisson, generate_preview_mesh
+    return solve_poisson, generate_preview_mesh
+
+
 class PoissonSimulationViewSet(viewsets.ModelViewSet):
     """ViewSet pour les simulations Poisson"""
     
@@ -26,6 +31,9 @@ class PoissonSimulationViewSet(viewsets.ModelViewSet):
         simulation = serializer.save(status='running')
         
         try:
+            # Lazy import solver
+            solve_poisson, _ = get_solver()
+            
             # Récupérer les paramètres
             params = simulation.get_parameters_dict()
             
@@ -91,6 +99,9 @@ class PoissonSimulationViewSet(viewsets.ModelViewSet):
     def preview_mesh(self, request):
         """Génère un aperçu du maillage sans résoudre l'équation"""
         try:
+            # Lazy import solver
+            _, generate_preview_mesh = get_solver()
+            
             # Construire les paramètres depuis la requête
             data = request.data
             params = {
@@ -121,6 +132,9 @@ class PoissonSimulationViewSet(viewsets.ModelViewSet):
         simulation.save()
         
         try:
+            # Lazy import solver
+            solve_poisson, _ = get_solver()
+            
             params = simulation.get_parameters_dict()
             result = solve_poisson(params)