feat(dc): Complete Tool C quick action buttons Phase 1-2 - 7 functions

Summary:
- Implement 7 quick action functions (filter, recode, binning, conditional, dropna, compute, pivot)
- Refactor to pre-written Python functions architecture (stable and secure)
- Add 7 Python operations modules with full type hints
- Add 7 frontend Dialog components with user-friendly UI
- Fix NaN serialization issues and auto type conversion
- Update all related documentation

Technical Details:
- Python: operations/ module (filter.py, recode.py, binning.py, conditional.py, dropna.py, compute.py, pivot.py)
- Backend: QuickActionService.ts with 7 execute methods
- Frontend: 7 Dialog components with complete validation
- Toolbar: Enable 7 quick action buttons

Status: Phase 1-2 completed, basic testing passed, ready for further testing

backend/src/modules/dc/tool-c/controllers/SessionController.ts

@@ -17,6 +17,7 @@ import { MultipartFile } from '@fastify/multipart';
 import { logger } from '../../../../common/logging/index.js';
 import { sessionService } from '../services/SessionService.js';
 import { dataProcessService } from '../services/DataProcessService.js';
+import * as xlsx from 'xlsx';
 
 // ==================== 请求参数类型定义 ====================
 
@@ -291,6 +292,76 @@ export class SessionController {
       });
     }
   }
+
+  /**
+   * ✨ 导出Excel文件（新增）
+   * 
+   * GET /api/v1/dc/tool-c/sessions/:id/export
+   */
+  async exportData(
+    request: FastifyRequest<{ Params: SessionIdParams }>,
+    reply: FastifyReply
+  ) {
+    try {
+      const { id } = request.params;
+
+      logger.info(`[SessionController] 导出Excel: ${id}`);
+
+      // 1. 获取Session信息
+      const session = await sessionService.getSession(id);
+
+      // 2. 获取完整数据
+      const data = await sessionService.getFullData(id);
+
+      // 3. 生成Excel
+      const workbook = xlsx.utils.book_new();
+      const worksheet = xlsx.utils.json_to_sheet(data);
+      
+      // 设置列宽（自动调整）
+      const colWidths = session.columns.map(col => {
+        const maxLength = Math.max(
+          col.length,
+          ...data.slice(0, 100).map(row => String(row[col] || '').length)
+        );
+        return { wch: Math.min(maxLength + 2, 50) };
+      });
+      worksheet['!cols'] = colWidths;
+      
+      xlsx.utils.book_append_sheet(workbook, worksheet, 'Data');
+
+      // 4. 生成Buffer
+      const buffer = xlsx.write(workbook, { 
+        type: 'buffer', 
+        bookType: 'xlsx',
+        compression: true,
+      });
+
+      // 5. 生成文件名（加上_cleaned后缀和时间戳）
+      const timestamp = new Date().toISOString().replace(/[:.]/g, '-').slice(0, 19);
+      const baseFileName = session.fileName.replace(/\.[^/.]+$/, ''); // 去除扩展名
+      const exportFileName = `${baseFileName}_cleaned_${timestamp}.xlsx`;
+
+      logger.info(`[SessionController] 导出成功: ${exportFileName}, 大小: ${(buffer.length / 1024).toFixed(2)}KB`);
+
+      // 6. 返回文件
+      reply.header('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+      reply.header('Content-Disposition', `attachment; filename="${encodeURIComponent(exportFileName)}"`);
+      reply.header('Content-Length', buffer.length);
+      
+      return reply.send(buffer);
+    } catch (error: any) {
+      logger.error(`[SessionController] 导出Excel失败: ${error.message}`);
+      
+      const statusCode = error.message.includes('不存在') || error.message.includes('过期') 
+        ? 404 
+        : 500;
+
+      return reply.code(statusCode).send({
+        success: false,
+        error: error.message || '导出Excel失败',
+      });
+    }
+  }
 }
 
 // ==================== 导出单例实例 ====================