ci: restore postgres durability-off settings in install.sh

The fan-out moved fsync/synchronous_commit/full_page_writes=off into
start-db.sh startup flags, but the Postgres workflow runs a postgres:13.3
service container and calls install.sh directly — it never runs start-db.sh.
So those flags never reached the Postgres CI, regressing it to full durability
on a commit-heavy suite. Re-apply them via ALTER SYSTEM (reloadable) in the
DB == "postgres" path, where the service-container workflow executes. MariaDB
is unaffected (DB != postgres).

.github/helper/install.sh

@@ -296,6 +296,15 @@ fi
 if [ "$DB" == "postgres" ];then
     echo "travis" | psql -h 127.0.0.1 -p 5432 -c "CREATE DATABASE test_frappe" -U postgres;
     echo "travis" | psql -h 127.0.0.1 -p 5432 -c "CREATE USER test_frappe WITH PASSWORD 'test_frappe'" -U postgres;
+
+    # Disposable CI DB: durability off for speed (postgres fsyncs every commit by default, which
+    # dominates a commit-heavy suite). All reloadable, no restart. The postgres workflow runs a
+    # service-container DB and never calls start-db.sh, so the flags must be applied here.
+    echo "travis" | psql -h 127.0.0.1 -p 5432 -U postgres \
+        -c "ALTER SYSTEM SET synchronous_commit = 'off'" \
+        -c "ALTER SYSTEM SET fsync = 'off'" \
+        -c "ALTER SYSTEM SET full_page_writes = 'off'" \
+        -c "SELECT pg_reload_conf()";
 fi
 
 cd ~/frappe-bench || exit