PostgREST empty-schema crash loop: apply the 3-statement fix, record before/after cycle count

PostgREST is crash-retrying every ~32s because this project has the Supabase Data API disabled, which leaves PostgREST looking for a schema named pg_pgrst_no_exposed_schemas that does not exist. Each cycle is a connection against a 60-connection ceiling (Nano: max_connections=60, shared_buffers=224MB, measured 2026-09-28). Origin: MARS-769 section 6.1, root-cause doc /data-venus/mars/ops/2026-09-28-supabase-saturation-findings.md, reference implementation db-mars-cc commit 6367dcb. Fix, three statements: create schema pgrst_no_exposed_schemas; alter role authenticator set pgrst.db_schemas = (that schema); notify pgrst. This is DDL, so it belongs to this project db lane, not to support-evolutiva-cc (SELECT only, fleet-wide). Deliverable: before/after postgrest_logs cycle count on this row. Instrument warning, measured both ways: the logs endpoint window argument behaves differently per project/session. On pluto the default window errored and an explicit iso_timestamp_start/end worked; on mars the default window worked and an explicit range returned Backend error. A Backend error is VOID, never a negative - retry the other form before concluding a project is clean.