feat(news): add opt-in Xquik search source

backend/.env.example

@@ -100,6 +100,15 @@ AIS_API_KEY=              # https://aisstream.io/ — free tier WebSocket key
 # configured news feeds (kill switch for the news layer).
 # NEWS_ENABLED=true
 
+# Xquik search for public X posts. Default off. NEWS_ENABLED=false also stops it.
+# Each poll may consume API credits. Configure one focused search query.
+# XQUIK_ENABLED=false
+# XQUIK_API_KEY=
+# XQUIK_SEARCH_QUERY=
+# XQUIK_SEARCH_LIMIT=20
+# XQUIK_SEARCH_INTERVAL_MINUTES=30
+# XQUIK_SEARCH_TIMEOUT_S=10
+
 # Global Fishing Watch — fishing vessel activity events (Fishing Activity map layer).
 # Free API token from https://globalfishingwatch.org/our-apis/tokens
 # Without this the fishing_activity layer stays empty.