fix(user): filter out soft-deleted memberships and organizations

Add get_active_memberships() method to User model that filters out
soft-deleted memberships and memberships of deleted organizations.
Update all usages of organization_memberships to use this method,
ensuring consistent handling of soft-deleted records across the
codebase. Also add deleted_at filters to CA queries in SSH helpers.

gatehouse_app/services/oidc/userinfo.py

@@ -55,9 +55,9 @@ def get_userinfo(access_token: str, validate_access_token_fn) -> Dict:
 
 def _get_user_roles(user: User) -> list:
     roles = []
-    if not user or not user.organization_memberships:
+    if not user:
         return roles
-    for member in user.organization_memberships:
+    for member in user.get_active_memberships():
         roles.append({
             "organization_id": str(member.organization_id),
             "role": member.role.value,