Refactor document handling and update Milvus collection settings

- Removed multiple failed document entries from `documents.json`.
- Added a new document entry with updated metadata and changed the index name to `regulations_dense_1024_v2`.
- Updated architecture documentation to reflect changes in the Milvus collection name.
- Adjusted requirements by removing the sqlalchemy dependency.
- Modified test cases to align with new document structure and naming conventions.
- Introduced a new test file for Milvus vector index runtime recovery and error handling.
- Updated assertions in various test files to ensure compatibility with the new schema.

backend/app/api/routes/rag.py

@@ -50,8 +50,8 @@ async def rag_chat(request: RagChatRequest):
                     {
                         "id": str(s.get("chunk_id") or s.get("doc_id") or idx + 1),
                         "score": s.get("score", 0),
-                        "preview": s.get("content", "")[:200],
-                        "doc_name": s.get("doc_name", ""),
+                        "preview": s.get("text", s.get("content", ""))[:200],
+                        "doc_name": s.get("doc_title", s.get("doc_name", "")),
                         "clause": s.get("section_title", "法规片段"),
                         "doc_id": s.get("doc_id"),
                         "download_url": (