birdnet-go: allow user-supplied /config/asound.conf override

Advanced users who legitimately need JACK, a custom dsnoop chain, or any
other ALSA setup can drop their own asound.conf into the addon config
folder. The cont-init script copies it over /etc/asound.conf before
launching the app, replacing the addon-shipped defaults.

birdnet-go/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## nightly-20260525-2 (26-05-2026)
 - Suppress noisy startup logs: silence `chmod /dev/snd` errors on the read-only HA mount, and hide unavailable ALSA plugins (JACK, OSS, dsnoop) from device enumeration so libjack and pcm_oss/dsnoop probes no longer print at launch.
+- Allow advanced users to override the addon's `/etc/asound.conf` by dropping a custom `asound.conf` into the addon config folder.
 
 ## nightly-20260525 (26-05-2026)
 - Minor bugs fixed

birdnet-go/rootfs/etc/cont-init.d/99-run.sh

@@ -8,6 +8,13 @@ set -e
 
 echo " "
 
+# Allow advanced users to supply their own /etc/asound.conf (e.g. to enable
+# JACK or a custom dsnoop chain) by dropping it into the addon config folder.
+if [ -f /config/asound.conf ]; then
+    bashio::log.info "Using user-provided /config/asound.conf, overriding addon defaults"
+    cp /config/asound.conf /etc/asound.conf
+fi
+
 # Check if alsa_card is provided
 CONFIG_LOCATION="/config/config.yaml"
 if bashio::config.true "homeassistant_microphone"; then