Removing a gated beta feature: flip the flag, keep the column dormant

When ungating a server-gated feature (search/beta behind a per-user boolean), do not drop the gating columns/tables — set the column DEFAULT to off, write one idempotent migration that flips existing rows (with a matching history/audit row), and leave the schema in place. That keeps the change reversible, preserves history, and leaves the gate as a future abuse lever. Critically, grep the WHOLE repo before declaring done: a single server-side flag ripples into terraform env vars, .env.example, Dockerfile comments, API-spec/README docs, and user-facing client copy — the code change is the small part.