chestshop hologram data layer: per-shop hologram flag + per-player preview preference

Part of PAR-166 (spin out /find). Data-layer gap for the hologram feature.

Legacy chestshop-database persists two things the holograms need that Treasury has no home for:

• Shop.hologram BOOLEAN — per-shop "show a floating item preview above this sign".
• PreviewPreference(player_id UUID PK, visible BOOLEAN) — per-player opt in/out of seeing previews.

Do (data layer only; rendering is a plugin-side sub-issue of PAR-166):

• New economy-schema migration: add hologram TINYINT(1) NOT NULL DEFAULT 1 to chestshop_shop, and a new chestshop_preview_preference(player_uuid_bin BINARY(16) PRIMARY KEY, visible TINYINT(1) NOT NULL DEFAULT 1) table.
• MarketApi methods to set per-shop hologram visibility and to get/set a player's preview preference (+ mappers).
• Plumb hologram through ChestShopShopRecord upsert (preserve on restock).
• Read API for the new plugin to fetch per-shop hologram flag + a player's preference.

Lower priority than the /find data gaps — holograms are the most cosmetic piece; can land after visibility/capacity/backfill.