Translate module docs to Chinese #1691

We currently have several English module documentation pages without Chinese counterparts. This issue is to translate them into Chinese while preserving the existing documentation structure and code examples.

Files to translate

Create Chinese versions for:

• docs/en/open_source/modules/model_backend.md
• docs/en/open_source/modules/mos/memos_mcp.md
• docs/en/open_source/modules/mos/memos_neo.md
• docs/en/open_source/modules/dream.md
• docs/en/open_source/modules/api_deployment.md

The translated files should be placed under the matching docs/cn/open_source/modules/ paths.

Requirements

• Keep all code blocks, commands, API names, class names, and file paths unchanged.
• Translate explanatory text into clear technical Chinese.
• Preserve the original headings and document structure unless a minor wording adjustment improves readability.
• Make sure links still point to valid pages after translation.

Acceptance Criteria

• Chinese docs exist for all files listed above.
• Markdown renders correctly.
• No code examples or command snippets are accidentally translated.
• The English and Chinese docs have matching structure.