fix(maintenance): run the measurement vacuum without a /dev/shm segment

docker-compose.yml

@@ -554,6 +554,10 @@ services:
       - shared_preload_libraries=pg_stat_statements
       - -c
       - pg_stat_statements.track=top
+    # Docker gives a container 64 MB of /dev/shm by default. Postgres keeps
+    # the shared memory of parallel queries and parallel maintenance there,
+    # and a larger plan fails with "could not resize shared memory segment".
+    shm_size: 256mb
     # cap_drop: [ALL] is deliberately NOT applied here (unlike `app`): the
     # official Postgres entrypoint starts as root, chowns the data
     # directory, and drops privileges to the `postgres` user itself, which