Client crash when connecting to a BDS via public IPv6, Xal auth URL parsing bug

Found this on a self-hosted BDS running with Host-mode networking on a VPS with a real public IPv6 address (not LAN/local). When IPv6 is exposed and the client picks the IPv6 route to connect (either through server list resolution or LAN discovery), the game crashes immediately on connect, before even reaching "Locating server". Doesn't happen when forcing IPv4.

Root cause:
The crash happens inside the Xbox Live auth signing flow, not in the BDS connection itself. The client tries to build a signing URL using the target server's IPv6 literal + port, but doesn't wrap it in brackets, so java throws:

java.lang.IllegalArgumentException: Invalid URL port: "4780:59:eb1::1:19133"

(should be [4780:59:eb1::1]:19133 per URL spec for IPv6 literals). This bubbles up and the app aborts with:

Abort message: 'JNI DETECTED ERROR IN APPLICATION: obj == null
    in call to CallVoidMethodV'
Fatal signal 6 (SIGABRT)

Native stack shows it's inside Xal::Auth::RequestSigner::HashRequest → Xal::Platform::Android::Sha256Java::AddBytes, called from GetTokenAndSignature.