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.

docs/architecture/aliyun-ingest-implementation.md

@@ -7,7 +7,7 @@
 - 上传入口保持为 `/api/v1/documents/upload`
 - 默认 `PARSER_BACKEND=aliyun`
 - 默认 `CHUNK_BACKEND=aliyun`
-- 默认 Milvus collection 为 `regulations_dense_1536_v2`
+- 默认 Milvus collection 为 `regulations_dense_1024_v2`
 - 解析产物落到 MinIO `artifacts/{doc_id}/`
 
 完整主链路如下：
@@ -19,7 +19,7 @@
 5. 转换为 `structure_nodes / semantic_blocks / vector_chunks`
 6. 三层结构 JSON 回写 MinIO
 7. 使用 `vector_chunks[*].embedding_text` 调 embedding API
-8. 写入 `regulations_dense_1536_v2`
+8. 写入 `regulations_dense_1024_v2`
 9. 文档状态更新为 `indexed`
 
 运行时转换逻辑位于 `backend/app/infrastructure/parser/aliyun_layout_normalizer.py`。