feat(auth): misc fediverse auth improvements

- remove automatic app validation
- add force refresh option to GetFediverseUrlAsync
- pass state to mastodon authorization URI

Foxnouns.Backend/Database/Models/FediverseApplication.cs

@@ -8,10 +8,6 @@ public class FediverseApplication : BaseModel
     public required string ClientId { get; set; }
     public required string ClientSecret { get; set; }
     public required FediverseInstanceType InstanceType { get; set; }
-
-    // These are for ensuring the application is still valid.
-    public string? AccessToken { get; set; }
-    public Instant? TokenValidUntil { get; set; }
 }
 
 public enum FediverseInstanceType