feat: add conf.d templates for AdGuard Home and Backrest

conf.d/backrest.conf.template

@@ -0,0 +1,12 @@
+server {
+    listen 443 ssl;
+    include snippets/https.conf;
+
+    server_name backrest.${BASE_DOMAIN};
+
+    include snippets/proxy.conf;
+
+    location / {
+        proxy_pass http://backrest:9898;
+    }
+}