Revert "fix: symlink /etc/dns to /config/dns at build time, drop entrypoint"

This reverts commit ed54778a0d.

technitium_dns/Dockerfile

@@ -1,9 +1,10 @@
+ARG BUILD_FROM=ghcr.io/hassio-addons/base:latest
 FROM technitium/dns-server:latest
 
 ENV DNS_SERVER_WEB_SERVICE_HTTPS_PORT=53443 \
     DNS_SERVER_WEB_SERVICE_ENABLE_HTTPS=false
 
-# Technitium hardcodes /etc/dns as its config dir. HA's addon_config mounts
-# at /config (persistent). Replace the real dir with a symlink so Technitium
-# writes through to the persistent volume.
-RUN rm -rf /etc/dns && mkdir -p /config/dns && ln -s /config/dns /etc/dns
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]