fix: point default client fileApi at self-hosted VPS mirror

Migrate client downloads off the external dandanton.com Nexus/CDN onto
http://159.75.5.225:19527/tdlm-client (nginx static, SHA-1 verified).

HMCL/src/main/java/org/jackhuang/hmcl/Metadata.java

@@ -141,9 +141,9 @@ public final class Metadata {
         return null;
     }
 
-    /// Default client Server Modpack fileApi: the Nexus raw repository `tdlm-client` read through the CDN host.
+    /// Default client Server Modpack fileApi: self-hosted static mirror on the TDLM VPS (nginx, port 19527).
     public static final String DEFAULT_CLIENT_FILE_API =
-            "https://maven.dandanton.com/repository/tdlm-client";
+            "http://159.75.5.225:19527/tdlm-client";
 
     /// Stable client update root (`server-manifest.json` and `overrides/` live under this URL).
     ///