feat: integrate SearXNG web search service with platform capabilities

- Added SearXNG service configuration to Docker setup, including environment variables and health checks.
- Introduced new settings management for web search in the frontend, allowing users to enable/disable and configure search engines and language preferences.
- Updated backend to support web search functionality, including database schema changes and service integration.
- Implemented health check endpoint for the web search service and integrated it into the application.
- Removed legacy SearXNG API connector references in favor of the new platform service approach.

docker/.env.example

@@ -36,6 +36,7 @@ EMBEDDING_MODEL=sentence-transformers/all-MiniLM-L6-v2
 # BACKEND_PORT=8929
 # FRONTEND_PORT=3929
 # ELECTRIC_PORT=5929
+# SEARXNG_PORT=8888
 # FLOWER_PORT=5555
 
 # ==============================================================================
@@ -199,6 +200,16 @@ STT_SERVICE=local/base
 # COMPOSIO_ENABLED=TRUE
 # COMPOSIO_REDIRECT_URI=http://localhost:8000/api/v1/auth/composio/connector/callback
 
+# ------------------------------------------------------------------------------
+# SearXNG (bundled web search — works out of the box, no config needed)
+# ------------------------------------------------------------------------------
+# SearXNG provides web search to all search spaces automatically.
+# To access the SearXNG UI directly: http://localhost:8888
+# To disable the service entirely: docker compose up --scale searxng=0
+# To point at your own SearXNG instance instead of the bundled one:
+# SEARXNG_DEFAULT_HOST=http://your-searxng:8080
+# SEARXNG_SECRET=surfsense-searxng-secret
+
 # ------------------------------------------------------------------------------
 # Daytona Sandbox (optional — cloud code execution for the deep agent)
 # ------------------------------------------------------------------------------