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/shared/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "extends": "@turbostarter/tsconfig/internal.json",
+  "compilerOptions": {},
+  "include": ["*.ts", "src/**/*"],
+  "exclude": ["node_modules"]
+}