feat(web): ddgs plugin (second migration)

Adds plugins/web/ddgs/ following the same plugins/image_gen/ pattern as
brave_free. DuckDuckGo search via the community ddgs package; no API key,
package is an optional dep gated by is_available().

E2E verified — registry now has ['brave-free', 'ddgs'].

plugins/web/ddgs/__init__.py

@@ -0,0 +1,15 @@
+"""DuckDuckGo search plugin — bundled, auto-loaded.
+
+Backed by the community ``ddgs`` Python package which scrapes DDG's HTML
+results page. No API key required, but the package itself must be installed
+(it's an optional dep — gated via :meth:`is_available`).
+"""
+
+from __future__ import annotations
+
+from plugins.web.ddgs.provider import DDGSWebSearchProvider
+
+
+def register(ctx) -> None:
+    """Register the DDGS provider with the plugin context."""
+    ctx.register_web_search_provider(DDGSWebSearchProvider())