Per-account database storage and current-month egress.

Composes account-wide DB storage and current-month egress (access_summary_daily) alongside the plan's storage limit, resolved server-side from plans.py. Storage comes from the same :func:_user_storage_rollup that answers /me/postgres/storage — the account page renders both into ONE sentence, so the two numbers must never disagree.

Storage is a SOFT cap: over-limit is surfaced as a warning on the account page and never blocks. Egress is a measurement only: the payload states the month's bytes and no allowance beside them, because no plan carries an egress figure. Returns 503 when the admin pool / config is unavailable (degraded mode) or when the storage rollup fails.

The route only reads the control DB, so it runs on run_read_in_thread. One statement reads the plan, _user_storage_targets adds one more, and the Postgres core reads the channels' rows in a third.