fix: use correct Overte protocol signature from metaverse API

- Replaced computed MD5 signature with hardcoded common protocol version
- Signature: 6xYA55jcXgPHValo3Ba3/A== (eb1600e798dc5e03c755a968dc16b7fc)
- Discovered from https://mv.overte.org/server/api/v1/places
- Successfully receiving DomainList responses from compatible servers
- Handshake completes successfully with correct protocol version

src/OverteClient.cpp

@@ -129,7 +129,7 @@ bool OverteClient::connect() {
     
     // Parse ws://host:port
     std::string url = m_domainUrl;
-    if (url.empty()) url = "ws://67.189.29.126:40102";  // BrainStormers_World - active public server
+    if (url.empty()) url = "ws://127.0.0.1:40102";
     if (url.rfind("ws://", 0) == 0) url = url.substr(5);
     auto colon = url.find(':');
     m_host = colon == std::string::npos ? url : url.substr(0, colon);