chore(backend): add roslynator and fix diagnostics

Foxnouns.Backend/Controllers/Authentication/AuthController.cs

@@ -38,7 +38,7 @@ public class AuthController(
         if (config.DiscordAuth is { ClientId: not null, ClientSecret: not null })
         {
             discord =
-                $"https://discord.com/oauth2/authorize?response_type=code"
+                "https://discord.com/oauth2/authorize?response_type=code"
                 + $"&client_id={config.DiscordAuth.ClientId}&scope=identify"
                 + $"&prompt=none&state={state}"
                 + $"&redirect_uri={HttpUtility.UrlEncode($"{config.BaseUrl}/auth/callback/discord")}";

Foxnouns.Backend/Controllers/Authentication/DiscordAuthController.cs

@@ -104,7 +104,7 @@ public class DiscordAuthController(
         );
 
         string url =
-            $"https://discord.com/oauth2/authorize?response_type=code"
+            "https://discord.com/oauth2/authorize?response_type=code"
             + $"&client_id={config.DiscordAuth.ClientId}&scope=identify"
             + $"&prompt=none&state={state}"
             + $"&redirect_uri={HttpUtility.UrlEncode($"{config.BaseUrl}/auth/callback/discord")}";

Foxnouns.Backend/Controllers/Authentication/EmailAuthController.cs

@@ -48,7 +48,9 @@ public class EmailAuthController(
                 ct
             )
         )
+        {
             return NoContent();
+        }
 
         mailService.QueueAccountCreationEmail(req.Email, state);
         return NoContent();