refactor: 重构 core 包目录结构并消除旧版 mod.rs

- 优化 剥离 models,algo 层并平铺业务模块
- 重构 统一使用现代 filename.rs + 文件夹结构替代旧版 mod.rs

ddddocr-tract/tests/char_slice.rs

@@ -2,8 +2,8 @@ use std::borrow::Cow;
 use std::fs::File;
 use std::path::Path;
 use anyhow::anyhow;
-use ddddocr_core::models::ocr::metadata::Charset;
-use ddddocr_core::models::ocr::metadata::{Normalization, Resize};
+use ddddocr_core::ocr::metadata::Charset;
+use ddddocr_core::ocr::metadata::{Normalization, Resize};
 
 pub const CHARSET_BETA: &[&str] = &[
     "", "笤", "谴", "膀", "荔", "佰", "电", "臁", "矍", "同", "奇", "芄", "吠", "6", "曛", "荇",