feat(knowledge): Phase B+C 文档提取器 + multipart 文件上传

- PDF 提取 (pdf-extract) + DOCX 提取 (zip+quick-xml) + Excel 解析 (calamine)
- 统一格式路由 detect_format() → RAG 通道或结构化通道
- POST /api/v1/knowledge/upload multipart 文件上传
- PDF/DOCX/Markdown → RAG 管线，Excel → structured_rows JSONB
- 结构化数据源 CRUD API (GET/DELETE /api/v1/structured/sources)
- POST /api/v1/structured/query JSONB 关键词查询
- 修复 industry/service.rs SaasError::Database 类型不匹配

crates/zclaw-saas/src/knowledge/mod.rs

@@ -3,6 +3,7 @@
 pub mod types;
 pub mod service;
 pub mod handlers;
+pub mod extractors;
 
 use axum::routing::{delete, get, patch, post, put};
 
@@ -20,6 +21,7 @@ pub fn routes() -> axum::Router<crate::state::AppState> {
         .route("/api/v1/knowledge/items", post(handlers::create_item))
         .route("/api/v1/knowledge/items/batch", post(handlers::batch_create_items))
         .route("/api/v1/knowledge/items/import", post(handlers::import_items))
+        .route("/api/v1/knowledge/upload", post(handlers::upload_file))
         .route("/api/v1/knowledge/items/:id", get(handlers::get_item))
         .route("/api/v1/knowledge/items/:id", put(handlers::update_item))
         .route("/api/v1/knowledge/items/:id", delete(handlers::delete_item))