provision-env-db: revoke PUBLIC connect on the OWNER database too

Revoking PUBLIC's CONNECT on the guest's own database is the half that does not
matter. A fresh Postgres database carries '=Tc' for PUBLIC — TEMP and CONNECT —
so as soon as a second role exists on the instance it can open a session against
every database still holding the default.

Provisioning beta and stopping there left thermograph_beta able to connect to
prod's database. The runbook's isolation check caught it on the live cutover;
this makes the script produce the state that check expects instead of a false
sense of it.

Grants the owner's read-only role an explicit CONNECT before the revoke, so the
ad-hoc query path (ops/dbq.sh, which connects as thermograph_ro) cannot lose
access to prod. The owner's app role owns the database and is a superuser, so it
is unaffected either way.

infra/deploy/RUNBOOK-vps1-vps2-cutover.md

@@ -149,8 +149,16 @@ it. That guard is why the superuser check above should never fail; run it
 anyway.
 
 If the first command SUCCEEDS, stop. `CONNECT` was not revoked and beta would be
-able to read production data; re-run the provisioning script and re-check before
+able to open a session against the production database; re-run the provisioning
-going further.
+script and re-check before going further.
+
+This is not hypothetical — it happened on the live cutover. The first version of
+the script revoked `PUBLIC` connect on the *guest's* database only, and a fresh
+Postgres database carries `=Tc` (TEMP **and** CONNECT) for `PUBLIC`, so
+`thermograph_beta` could still reach `thermograph`. The script now hardens the
+owner's database too, granting the owner's read-only role an explicit `CONNECT`
+first so the revoke cannot strip `ops/dbq.sh` of its access. The check above is
+what caught it.
 
 **Rollback:** `DROP DATABASE thermograph_beta; DROP ROLE thermograph_beta;` —
 prod is unaffected either way.

infra/deploy/db/provision-env-db.sh

@@ -156,6 +156,46 @@ ALTER DEFAULT PRIVILEGES FOR ROLE :"role" IN SCHEMA public
   GRANT SELECT ON SEQUENCES TO :"rorole";
 SQL
 
+# --- harden the OWNER environment's database too -------------------------------
+#
+# Revoking CONNECT from PUBLIC on the guest's own database is only half the job,
+# and the missing half is the half that matters. A fresh Postgres database
+# carries `=Tc` for PUBLIC — TEMP *and* CONNECT — so the moment a second role
+# exists on the instance, that role can connect to every database that still has
+# the default. Provisioning beta and stopping here left `thermograph_beta` able
+# to open a session against prod's database; caught live by the runbook's own
+# isolation check, which is why that check exists.
+#
+# Order matters: grant the owner's read-only role an EXPLICIT connect first, so
+# the revoke below cannot strip the ad-hoc query path (ops/dbq.sh) of its access.
+# The owner's app role is the database owner and a superuser, so it is unaffected
+# either way.
+OWNER_DB=$(
+  # shellcheck disable=SC1090 # sourced above; re-resolving prod in a subshell
+  thermograph_topology prod >/dev/null 2>&1
+  printf '%s' "$TG_DB_NAME"
+)
+OWNER_RO=$(
+  thermograph_topology prod >/dev/null 2>&1
+  printf '%s_ro' "$TG_DB_USER"
+)
+# Restore this run's environment — thermograph_topology overwrote the TG_* vars.
+thermograph_topology "$ENV_NAME"
+
+if [ "$OWNER_DB" != "$TG_DB_NAME" ]; then
+  echo "==> Hardening the owner database '${OWNER_DB}' against PUBLIC connects"
+  docker exec -i "$DB_CID" \
+    psql -v ON_ERROR_STOP=1 -U thermograph -d postgres \
+         -v ownerdb="$OWNER_DB" -v ownerro="$OWNER_RO" <<'SQL'
+-- Only if that read-only role actually exists (it predates this script).
+SELECT format('GRANT CONNECT ON DATABASE %I TO %I', :'ownerdb', :'ownerro')
+WHERE EXISTS (SELECT 1 FROM pg_roles WHERE rolname = :'ownerro')
+\gexec
+
+REVOKE CONNECT ON DATABASE :"ownerdb" FROM PUBLIC;
+SQL
+fi
+
 echo "==> OK: ${TG_DB_USER} owns ${TG_DB_NAME} (timescaledb enabled, PUBLIC revoked)"
 echo "    Verify isolation:"
 echo "      docker exec $DB_CID psql -U ${TG_DB_USER} -d thermograph -c 'select 1'   # must FAIL"