🔧 Add LLM prompt file for Simplified Chinese, generated from the existing translations (#14549)

Co-authored-by: 史雲昔 (Vincy SHI) <vincy@vincy1230.net>

docs/zh/llm-prompt.md

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+### Target language
+
+Translate to Simplified Chinese (简体中文).
+
+Language code: zh.
+
+### Grammar and tone
+
+1) Use clear, concise technical Chinese consistent with existing docs.
+2) Address the reader naturally (commonly using “你/你的”).
+
+### Headings
+
+1) Follow existing Simplified Chinese heading style (short and descriptive).
+2) Do not add trailing punctuation to headings.
+3) If a heading contains only the name of a FastAPI feature, do not translate it.
+
+### Quotes and punctuation
+
+1) Keep punctuation style consistent with existing Simplified Chinese docs (they often mix English terms like “FastAPI” with Chinese text).
+2) Never change punctuation inside inline code, code blocks, URLs, or file paths.
+
+### Ellipsis
+
+1) Keep ellipsis style consistent within each document, prefer `...` over  `……`.
+2) Never change ellipsis in code, URLs, or CLI examples.
+
+### Preferred translations / glossary
+
+Use the following preferred translations when they apply in documentation prose:
+
+- request (HTTP): 请求
+- response (HTTP): 响应
+- path operation: 路径操作
+- path operation function: 路径操作函数
+
+### `///` admonitions
+
+1) Keep the admonition keyword in English (do not translate `note`, `tip`, etc.).
+2) If a title is present, prefer these canonical titles:
+
+- `/// tip | 提示`
+- `/// note | 注意`
+- `/// warning | 警告`
+- `/// info | 信息`
+- `/// danger | 危险`