Adds a per-collective curation knob on top of the existing use_count
ordering. The UI exposes a 3-way Hide/Normal/Boost control that writes
weight=-50/0/50 via the new SECURITY DEFINER RPC; the column itself is
unconstrained so a future granularity tier doesn't need a schema diff.
Both new RPCs (set_item_frequency_weight, purge_item_frequency) gate on
collective_members.role='admin'. The all-deny RLS from migration 006 is
preserved — the RPCs are the only write path. The trigger that fires on
shopping_items INSERT keeps backfilling weight=0 via the column default.
Re-create the suggestion index to lead with weight DESC so the dropdown
query can scan in order without a sort step.
pgTAP test 018 covers the column/index/RPC schema invariants + the
default-from-trigger behaviour (11 assertions). Role-gate denial-for-non-
admin is covered by the Vitest integration suite (next commit) — pgTAP
runs as postgres so the auth.uid() guard can't be exercised here.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
