Check for "rimworld-mod" topic to filter public repos

Models/RemoteRepo.cs

@@ -7,5 +7,6 @@ public record RemoteRepo(
     [property: JsonPropertyName("clone_url")] string CloneUrl,
     [property: JsonPropertyName("default_branch")] string DefaultBranch,
     [property: JsonPropertyName("description")] string? Description,
-    [property: JsonPropertyName("html_url")] string HtmlUrl
+    [property: JsonPropertyName("html_url")] string HtmlUrl,
+    [property: JsonPropertyName("topics")] IReadOnlyList<string> Topics
 );

Services/GitHubApiService.cs

@@ -7,6 +7,7 @@ public class GitHubApiService : IGitHubApiService, IDisposable
 {
     private const string OrgName = "FalloutCollaborationProject";
     private const string BaseUrl = "https://api.github.com";
+    private const string RequiredTopic = "rimworld-mod";
 
     private readonly HttpClient _httpClient;
     private readonly TimeSpan _cacheExpiry = TimeSpan.FromHours(1);
@@ -86,7 +87,10 @@ public class GitHubApiService : IGitHubApiService, IDisposable
 
         if (allRepos.Count > 0)
         {
-            _cachedRepos = allRepos;
+            // Filter to only repos tagged as RimWorld mods
+            _cachedRepos = allRepos
+                .Where(r => r.Topics.Contains(RequiredTopic, StringComparer.OrdinalIgnoreCase))
+                .ToList();
             _cacheTime = DateTimeOffset.UtcNow;
         }