Add search layer: Kiwix offline docs + DuckDuckGo web search

The model can now search before it generates:

MCP tools (available via Open WebUI + Claude Code):
- search_docs(query): searches Kiwix ZIM files (Wikipedia, Stack Overflow,
  DevDocs, Arch Wiki) — instant, offline, no rate limits
- read_doc(path): reads full article content from Kiwix results
- web_search(query): DuckDuckGo search, no API key needed

Open WebUI native search:
- ENABLE_RAG_WEB_SEARCH=true + RAG_WEB_SEARCH_ENGINE=duckduckgo
- Switched from SearXNG (not in stack) to DDG (zero config)

Search priority: Kiwix first (offline, fast) → DDG fallback (live web)

All 3 setup scripts updated:
- duckduckgo-search added to mcp_requirements.txt
- KIWIX_URL=http://kiwix:80 added to MCP container env
- curl added to MCP container deps (for sync script)
- Open WebUI DDG search enabled by default

https://claude.ai/code/session_01PtYTPherSJaxDEVPgF6Nxu

ubuntu-post-install.sh

@@ -1572,6 +1572,7 @@ mcp[cli]
 fastapi
 uvicorn[standard]
 httpx
+duckduckgo-search
 REQ
 ok "requirements.txt + mcp_requirements.txt"
 
@@ -1651,7 +1652,7 @@ services:
       - OPENAI_API_KEY=local-rag
       - ENABLE_OPENAI_API=true
       - ENABLE_RAG_WEB_SEARCH=true
-      - RAG_WEB_SEARCH_ENGINE=searxng
+      - RAG_WEB_SEARCH_ENGINE=duckduckgo
       - SEARXNG_QUERY_URL=http://searxng:8080/search?q=<query>&format=json
       - WEBUI_AUTH=false
     depends_on:
@@ -1712,8 +1713,9 @@ services:
       - REPOS_DIR=/repos
       - GITEA_URL=http://gitea:3000
       - RAG_URL=http://rag-server:8001
+      - KIWIX_URL=http://kiwix:80
     command: >
-      bash -c "apt-get update -qq && apt-get install -y --no-install-recommends git ripgrep &&
+      bash -c "apt-get update -qq && apt-get install -y --no-install-recommends git ripgrep curl &&
                pip install --no-cache-dir -r mcp_requirements.txt &&
                python mcp_server.py"
     depends_on: [rag-server]