Add UDP buffer sysctl config for QUIC performance

Increases net.core.rmem_max and net.core.wmem_max to 7.5MB as
recommended by quic-go for high-bandwidth QUIC transfers.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: shanemcd

mybox/Containerfile

@@ -113,6 +113,7 @@ EORUN
 # =============================================================================
 # Note: Cursor and 1Password GUI are installed via sysext, see docs/SYSEXTS.md
 COPY files/00-keyboard.conf /etc/X11/xorg.conf.d/00-keyboard.conf
+COPY files/99-udp-buffers.conf /etc/sysctl.d/99-udp-buffers.conf
 COPY files/apcupsd.conf /etc/apcupsd/apcupsd.conf
 
 RUN <<EORUN

mybox/files/99-udp-buffers.conf

@@ -0,0 +1,4 @@
+# Increase UDP buffer sizes for QUIC performance
+# See: https://github.com/quic-go/quic-go/wiki/UDP-Buffer-Sizes
+net.core.rmem_max=7500000
+net.core.wmem_max=7500000