feat: Add SearXNG for improved web search

- Add SearXNG service to docker-compose.yml (port 11112)
- Add SEARXNG_SECRET_KEY to .env.example
- Add searxng-data/settings.yml with FR engines (google, bing, ddg, qwant)
- Add docs/SEARXNG-INTEGRATION.md with OpenWebUI tool setup

docker-compose.yml

@@ -5,6 +5,24 @@
 
 services:
 
+  # ─────────────────────────────────────────────────────────
+  # 0. SEARXNG - Meta-search Engine (Web Search)
+  #    → http://192.168.1.27:11112
+  # ─────────────────────────────────────────────────────────
+  searxng:
+    image: searxng/searxng:latest
+    container_name: effi-searxng
+    restart: unless-stopped
+    ports:
+      - "11112:8080"
+    volumes:
+      - ./searxng-data:/etc/searxng:rw
+    environment:
+      - SEARXNG_BASE_URL=http://192.168.1.27:11112/
+      - SEARXNG_SECRET=${SEARXNG_SECRET_KEY}
+    networks:
+      - effi-net
+
   # ─────────────────────────────────────────────────────────
   # 1. OPEN WEBUI - Interface Chat Effi
   #    → http://192.168.1.27:3000