fix: finalize weekly postgres backup retention

infra/postgres-backup.sh

@@ -2,8 +2,8 @@
 set -eu
 umask 077
 
-app_dir=/srv/miem_workers
-backup_dir=/home/codex/backups/postgres
+app_dir=$(CDPATH= cd -- "$(dirname "$0")/.." && pwd)
+backup_dir="$HOME/backups/postgres"
 backup="$backup_dir/postgres-latest.sql"
 temporary="$backup.tmp.$$"
 
@@ -14,5 +14,5 @@ cd "$app_dir"
 docker compose exec -T postgres sh -c 'pg_dumpall -U "$POSTGRES_USER"' > "$temporary"
 test -s "$temporary"
 mv "$temporary" "$backup"
-find /home/codex/backups/miem_workers -maxdepth 1 -type f -name 'miem_workers-*.sql' -delete 2>/dev/null || true
+find "$HOME/backups/miem_workers" -maxdepth 1 -type f -name 'miem_workers-*.sql' -delete 2>/dev/null || true
 printf '%s\n' "Created $backup"