Add IntelliJ IDEA project configuration files

This commit adds IntelliJ IDEA-specific configuration files for the project, including module setup, version control integration, inspection profiles, and workspace settings. These files facilitate development environment configuration for contributors using IntelliJ IDEA.

accounts/backends.py

@@ -0,0 +1,16 @@
+from django.contrib.auth.backends import ModelBackend
+
+
+class CompanyUserBackend(ModelBackend):
+    def get_user_permissions(self, user_obj, obj=None):
+        if not user_obj.is_active or user_obj.is_anonymous:
+            return set()
+
+        if user_obj.is_superuser:
+            return super().get_user_permissions(user_obj, obj)
+
+        perms = super().get_user_permissions(user_obj, obj)
+        if user_obj.company and user_obj.company.is_client:
+            # Filter permissions based on client company context
+            perms = {p for p in perms if p.startswith('accounts.client_')}
+        return perms