v2.3.4 — Fix BBS splash encoding in cmd.exe

Fix: BBS startup splash rendered as blank lines on Server 2016 / older conhost when launched via upd.cmd. PowerShell inherited cmd.exe's CP437/CP1252 console encoding, stripping Unicode block-drawing chars (U+2588, U+2557, U+2550, etc.).

Now forces UTF-8 console I/O at script start ([Console]::OutputEncoding + chcp 65001) so block/box-drawing chars survive the cmd.exe → pwsh handoff. Tested on Windows Server 2016.