fix: explicitly set sids to null so the find free sid functions actually trigger

Foxnouns.Backend/Controllers/MembersController.cs

@@ -94,6 +94,7 @@ public class MembersController(
             Names = req.Names ?? [],
             Pronouns = req.Pronouns ?? [],
             Unlisted = req.Unlisted ?? false,
+            Sid = null!,
         };
         db.Add(member);
 

Foxnouns.Backend/Services/Auth/AuthService.cs

@@ -45,6 +45,7 @@ public class AuthService(
                 },
             },
             LastActive = clock.GetCurrentInstant(),
+            Sid = null!,
         };
 
         db.Add(user);
@@ -88,6 +89,7 @@ public class AuthService(
                 },
             },
             LastActive = clock.GetCurrentInstant(),
+            Sid = null!,
         };
 
         db.Add(user);