UTXO Wallet Windows Web Search Module

Purpose:
- Add a Windows-only web search section to the wallet app.
- Use a DuckDuckGo-style clean UX while preferring an open-source SearXNG-compatible search URL.
- Avoid search API integrations and avoid paid API keys.

Security:
- No search API key is included.
- No 0x or LI.FI key is included.
- No seed phrase or private key is included.
- Only HTTPS search URLs are accepted.
- External open mode is default because many search sites block iframes.
- The browser module is isolated from wallet signing and swap execution.

Production recommendation:
- Use your own SearXNG instance later for maximum control.
- Keep search separate from the Cloudflare swap Worker.
