feat(db): mesh data model — meshes, members, invites, audit log

- pgSchema "mesh" with 4 tables isolating the peer mesh domain
- Enums: visibility, transport, tier, role
- audit_log is metadata-only (E2E encryption enforced at broker/client)
- Cascade on mesh delete, soft-delete via archivedAt/revokedAt

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

packages/ui/shared/src/utils/index.ts

@@ -0,0 +1,6 @@
+import { cx } from "class-variance-authority";
+import { twMerge } from "tailwind-merge";
+
+const cn = (...inputs: Parameters<typeof cx>) => twMerge(cx(inputs));
+
+export { cn };