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/industry/service.rs

@@ -196,14 +196,14 @@ pub async fn set_account_industries(
     .bind(&ids)
     .fetch_one(pool)
     .await
-    .map_err(|e| SaasError::Database(e.to_string()))?;
+    .map_err(SaasError::Database)?;
 
     if valid_count.0 != ids.len() as i64 {
         return Err(SaasError::InvalidInput("部分行业不存在或已禁用".to_string()));
     }
 
     // 事务性 DELETE + INSERT
-    let mut tx = pool.begin().await.map_err(|e| SaasError::Database(e.to_string()))?;
+    let mut tx = pool.begin().await.map_err(SaasError::Database)?;
 
     sqlx::query("DELETE FROM account_industries WHERE account_id = $1")
         .bind(account_id)
@@ -223,7 +223,7 @@ pub async fn set_account_industries(
         .await?;
     }
 
-    tx.commit().await.map_err(|e| SaasError::Database(e.to_string()))?;
+    tx.commit().await.map_err(SaasError::Database)?;
 
     list_account_industries(pool, account_id).await
 }