Replace sequential proxy fallback (up to 30s worst-case) with concurrent
racing via futures::select_ok, returning the first successful response.
Add list_installed_agents_local command for instant UI rendering with
async registry update. Fix missing useToast import in RedisValueViewer.
Add hwdns.net and gh-proxy.org as proxy fallbacks before direct GitHub
access, with 10s timeout per endpoint. Significantly improves update
check speed in regions with slow GitHub connectivity.
Refactor all database drivers, query execution, schema operations, and
business logic into a shared `dbx-core` crate. The Tauri desktop app
becomes a thin shell delegating to dbx-core, enabling future web and
CLI frontends to reuse the same core.
skyler