feat: migrate setup visibility from boolean to three-tier system

Replace isPublic boolean with visibility enum (private/link/public) across
the full stack. Add shares table to schema for future share link support.
Update all services, routes, schemas, hooks, components, and tests.

Plan: 32-01 (Setup Sharing System - Schema Migration)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/components/SetupsView.tsx

@@ -100,7 +100,7 @@ export function SetupsView() {
 							key={setup.id}
 							id={setup.id}
 							name={setup.name}
-							isPublic={setup.isPublic}
+							visibility={setup.visibility}
 							itemCount={setup.itemCount}
 							totalWeight={setup.totalWeight}
 							totalCost={setup.totalCost}