feat: integrate RAG rag_jrxml submodule and fix Anthropic API key

Add rag submodule for semantic JRXML chunk retrieval, refactor
retrieve node to use RAGSearcher, and fix missing api_key in
Anthropic SDK client initialization.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/llm.py

@@ -28,7 +28,7 @@ def get_llm():
 
         os.environ["NO_PROXY"] = "*"
 
-        client = Anthropic(base_url=base_url, timeout=120)
+        client = Anthropic(api_key=api_key, base_url=base_url, timeout=120)
 
         class MiniMaxLLM:
             def invoke(self, prompt: str) -> Any: