feat(dc/tool-c): Add missing value imputation feature with 6 methods and MICE

Major features:
1. Missing value imputation (6 simple methods + MICE):
   - Mean/Median/Mode/Constant imputation
   - Forward fill (ffill) and Backward fill (bfill) for time series
   - MICE multivariate imputation (in progress, shape issue to fix)

2. Auto precision detection:
   - Automatically match decimal places of original data
   - Prevent false precision (e.g. 13.57 instead of 13.566716417910449)

3. Categorical variable detection:
   - Auto-detect and skip categorical columns in MICE
   - Show warnings for unsuitable columns
   - Suggest mode imputation for categorical data

4. UI improvements:
   - Rename button: "Delete Missing" to "Missing Value Handling"
   - Remove standalone "Dedup" and "MICE" buttons
   - 3-tab dialog: Delete / Fill / Advanced Fill
   - Display column statistics and recommended methods
   - Extended warning messages (8 seconds for skipped columns)

5. Bug fixes:
   - Fix sessionService.updateSessionData -> saveProcessedData
   - Fix OperationResult interface (add message and stats)
   - Fix Toolbar button labels and removal

Modified files:
Python: operations/fillna.py (new, 556 lines), main.py (3 new endpoints)
Backend: QuickActionService.ts, QuickActionController.ts, routes/index.ts
Frontend: MissingValueDialog.tsx (new, 437 lines), Toolbar.tsx, index.tsx
Tests: test_fillna_operations.py (774 lines), test scripts and docs
Docs: 5 documentation files updated

Known issues:
- MICE imputation has DataFrame shape mismatch issue (under debugging)
- Workaround: Use 6 simple imputation methods first

Status: Development complete, MICE debugging in progress
Lines added: ~2000 lines across 3 tiers

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

@@ -389,6 +389,156 @@ export class QuickActionController {
       });
     }
   }
+  
+  /**
+   * POST /api/v1/dc/tool-c/fillna/stats
+   * 获取列的缺失值统计
+   */
+  async handleGetFillnaStats(request: FastifyRequest, reply: FastifyReply) {
+    try {
+      const { sessionId, column } = request.body as { sessionId: string; column: string };
+      
+      logger.info(`[QuickAction] 获取缺失值统计: session=${sessionId}, column=${column}`);
+      
+      // 获取Session数据
+      const fullData = await sessionService.getFullData(sessionId);
+      
+      // 调用Service获取统计
+      const result = await quickActionService.getFillnaStats(fullData, column);
+      
+      if (!result.success) {
+        return reply.code(500).send({
+          success: false,
+          error: result.error
+        });
+      }
+      
+      return reply.code(200).send({
+        success: true,
+        stats: result.stats,
+        execution_time: result.execution_time
+      });
+      
+    } catch (error: any) {
+      logger.error(`[QuickAction] 获取统计失败: ${error.message}`);
+      return reply.code(500).send({
+        success: false,
+        error: error.message
+      });
+    }
+  }
+  
+  /**
+   * POST /api/v1/dc/tool-c/fillna/simple
+   * 执行简单填补
+   */
+  async handleFillnaSimple(request: FastifyRequest, reply: FastifyReply) {
+    try {
+      const { sessionId, column, newColumnName, method, fillValue } = request.body as {
+        sessionId: string;
+        column: string;
+        newColumnName: string;
+        method: string;
+        fillValue?: any;
+      };
+      
+      logger.info(`[QuickAction] 执行简单填补: session=${sessionId}, method=${method}, column=${column}`);
+      
+      // 获取Session数据
+      const fullData = await sessionService.getFullData(sessionId);
+      
+      // 调用Service执行填补
+      const result = await quickActionService.executeFillnaSimple(fullData, {
+        column,
+        newColumnName,
+        method: method as any,
+        fillValue
+      });
+      
+      if (!result.success) {
+        return reply.code(500).send({
+          success: false,
+          error: result.error
+        });
+      }
+      
+      // 更新Session数据
+      const resultData = result.result_data || [];
+      await sessionService.saveProcessedData(sessionId, resultData);
+      
+      return reply.code(200).send({
+        success: true,
+        data: {
+          newDataPreview: resultData.slice(0, 50),
+          affectedRows: resultData.length,
+          message: result.message || '填补成功',
+          stats: result.stats
+        }
+      });
+      
+    } catch (error: any) {
+      logger.error(`[QuickAction] 简单填补失败: ${error.message}`);
+      return reply.code(500).send({
+        success: false,
+        error: error.message
+      });
+    }
+  }
+  
+  /**
+   * POST /api/v1/dc/tool-c/fillna/mice
+   * 执行MICE多重插补
+   */
+  async handleFillnaMice(request: FastifyRequest, reply: FastifyReply) {
+    try {
+      const { sessionId, columns, nIterations, randomState } = request.body as {
+        sessionId: string;
+        columns: string[];
+        nIterations?: number;
+        randomState?: number;
+      };
+      
+      logger.info(`[QuickAction] 执行MICE填补: session=${sessionId}, columns=${columns.length}个`);
+      
+      // 获取Session数据
+      const fullData = await sessionService.getFullData(sessionId);
+      
+      // 调用Service执行MICE填补
+      const result = await quickActionService.executeFillnaMice(fullData, {
+        columns,
+        nIterations,
+        randomState
+      });
+      
+      if (!result.success) {
+        return reply.code(500).send({
+          success: false,
+          error: result.error
+        });
+      }
+      
+      // 更新Session数据
+      const resultData = result.result_data || [];
+      await sessionService.saveProcessedData(sessionId, resultData);
+      
+      return reply.code(200).send({
+        success: true,
+        data: {
+          newDataPreview: resultData.slice(0, 50),
+          affectedRows: resultData.length,
+          message: result.message || 'MICE填补成功',
+          stats: result.stats
+        }
+      });
+      
+    } catch (error: any) {
+      logger.error(`[QuickAction] MICE填补失败: ${error.message}`);
+      return reply.code(500).send({
+        success: false,
+        error: error.message
+      });
+    }
+  }
 }
 
 // ==================== 导出单例 ====================

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

@@ -228,3 +228,5 @@ export const streamAIController = new StreamAIController();
 
 
 
+
+