Improve URL matching and handle 404 on indexer removal

- Use path-boundary check in GetIndexerMappings to prevent prefix
  false matches on ProwlarrUrl
- Treat 404 as success in RemoveIndexer so local cleanup proceeds
  when the remote indexer is already gone

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/NzbDrone.Core/Applications/Qui/Qui.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using FluentValidation.Results;
@@ -39,8 +40,11 @@ public override List<AppIndexerMap> GetIndexerMappings()
 
             foreach (var indexer in indexers)
             {
+                var baseUrl = Settings.ProwlarrUrl.TrimEnd('/');
+
                 if (indexer.Backend == "prowlarr" &&
-                    indexer.BaseUrl?.TrimEnd('/').StartsWith(Settings.ProwlarrUrl.TrimEnd('/')) == true &&
+                    (indexer.BaseUrl?.TrimEnd('/').Equals(baseUrl, StringComparison.OrdinalIgnoreCase) == true ||
+                     indexer.BaseUrl?.StartsWith(baseUrl + "/", StringComparison.OrdinalIgnoreCase) == true) &&
                     indexer.ApiKey == _configFileProvider.ApiKey &&
                     int.TryParse(indexer.IndexerId, out var indexerId))
                 {

src/NzbDrone.Core/Applications/Qui/QuiProxy.cs

@@ -84,6 +84,11 @@ public void RemoveIndexer(int indexerId, QuiSettings settings)
             var request = BuildRequest(settings, $"{AppIndexerApiRoute}/{indexerId}", HttpMethod.Delete);
             var response = _httpClient.Execute(request);
 
+            if (response.StatusCode == HttpStatusCode.NotFound)
+            {
+                return;
+            }
+
             if ((int)response.StatusCode >= 300)
             {
                 throw new HttpException(response);