fix(Server): add missing /Upgrade/Report route

The server registers both /Upgrade/Verification and /Update/Verification
but only /Update/Report for status reporting. Add /Upgrade/Report so
clients using the /Upgrade/* URL variant can report update status.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: JusterZhu

src/Server/Program.cs

@@ -119,6 +119,7 @@
 };
 
 app.MapPost("/Update/Report", handleReport);
+app.MapPost("/Upgrade/Report", handleReport);
 
 // ──  GET /File/Download/{hash}  ───────────────────────────────────
 // Serves package files by their SHA256 hash. Supports HTTP Range