feat(dc/tool-c): Add pivot column ordering and NA handling features

Major features:
1. Pivot transformation enhancements:
   - Add option to keep unselected columns with 3 aggregation methods
   - Maintain original column order after pivot (aligned with source file)
   - Preserve pivot value order (first appearance order)

2. NA handling across 4 core functions:
   - Recode: Support keep/map/drop for NA values
   - Filter: Already supports is_null/not_null operators
   - Binning: Support keep/label/assign for NA values (fix nan display)
   - Conditional: Add is_null/not_null operators

3. UI improvements:
   - Enable column header tooltips with custom header component
   - Add closeable alert for 50-row preview
   - Fix page scrollbar issues

Modified files:
Python: pivot.py, recode.py, binning.py, conditional.py, main.py
Backend: SessionController, QuickActionController, QuickActionService
Frontend: PivotDialog, RecodeDialog, BinningDialog, ConditionalDialog, DataGrid, index

Status: Ready for testing

backend/src/modules/dc/tool-c/services/QuickActionService.ts

@@ -27,6 +27,8 @@ interface RecodeParams {
   mapping: Record<string, any>;
   createNewColumn: boolean;
   newColumnName?: string;
+  naHandling?: 'keep' | 'map' | 'drop';  // ✨ 新增：NA处理方式
+  naValue?: any;  // ✨ 新增：NA映射值
 }
 
 interface BinningParams {
@@ -36,6 +38,9 @@ interface BinningParams {
   bins?: number[];
   labels?: (string | number)[];
   numBins?: number;
+  naHandling?: 'keep' | 'label' | 'assign';  // ✨ 新增：NA处理方式
+  naLabel?: string;  // ✨ 新增：NA标签
+  naAssignTo?: number;  // ✨ 新增：NA分配到的组索引
 }
 
 interface ConditionalParams {
@@ -68,6 +73,8 @@ interface PivotParams {
   pivotColumn: string;
   valueColumns: string[];
   aggfunc: 'first' | 'last' | 'mean' | 'sum' | 'min' | 'max';
+  keepUnusedColumns?: boolean;  // ✨ 新增：是否保留未选择的列
+  unusedAggMethod?: 'first' | 'mode' | 'mean';  // ✨ 新增：未选择列的聚合方式
 }
 
 interface OperationResult {
@@ -128,6 +135,8 @@ export class QuickActionService {
         mapping: params.mapping,
         create_new_column: params.createNewColumn,
         new_column_name: params.newColumnName,
+        na_handling: params.naHandling || 'keep',  // ✨ NA处理方式
+        na_value: params.naValue,  // ✨ NA映射值
       }, {
         timeout: 60000,
       });
@@ -164,6 +173,9 @@ export class QuickActionService {
         bins: params.bins,
         labels: params.labels,
         num_bins: params.numBins,
+        na_handling: params.naHandling || 'keep',  // ✨ NA处理方式
+        na_label: params.naLabel,  // ✨ NA标签
+        na_assign_to: params.naAssignTo,  // ✨ NA分配到的组索引
       }, {
         timeout: 60000,
       });
@@ -254,14 +266,16 @@ export class QuickActionService {
   /**
    * 执行计算列
    */
-  async executeCompute(data: any[], params: ComputeParams): Promise<OperationResult> {
+  async executeCompute(data: any[], params: ComputeParams, columnMapping?: any[]): Promise<OperationResult> {
     try {
       logger.info(`[QuickActionService] 调用计算列API: ${params.newColumnName}, formula=${params.formula}`);
       
+      // ✨ 传递columnMapping给Python（方案B：Python负责替换）
       const response = await axios.post(`${PYTHON_SERVICE_URL}/api/operations/compute`, {
         data,
         new_column_name: params.newColumnName,
         formula: params.formula,
+        column_mapping: columnMapping || [], // ✨ 传递列名映射
       }, {
         timeout: 60000,
       });
@@ -286,16 +300,28 @@ export class QuickActionService {
   /**
    * 执行Pivot（长表→宽表）
    */
-  async executePivot(data: any[], params: PivotParams): Promise<OperationResult> {
+  async executePivot(
+    data: any[], 
+    params: PivotParams, 
+    columnMapping?: any[], 
+    originalColumnOrder?: string[],
+    pivotValueOrder?: string[]
+  ): Promise<OperationResult> {
     try {
       logger.info(`[QuickActionService] 调用Pivot API: ${params.indexColumn} × ${params.pivotColumn}`);
       
+      // ✨ 传递columnMapping、未选择列处理参数和列顺序给Python
       const response = await axios.post(`${PYTHON_SERVICE_URL}/api/operations/pivot`, {
         data,
         index_column: params.indexColumn,
         pivot_column: params.pivotColumn,
         value_columns: params.valueColumns,
         aggfunc: params.aggfunc,
+        column_mapping: columnMapping || [], // ✨ 传递列名映射
+        keep_unused_columns: params.keepUnusedColumns || false,  // ✨ 是否保留未选择的列
+        unused_agg_method: params.unusedAggMethod || 'first',  // ✨ 未选择列的聚合方式
+        original_column_order: originalColumnOrder || [],  // ✨ 原始列顺序
+        pivot_value_order: pivotValueOrder || [],  // ✨ 透视列值的原始顺序
       }, {
         timeout: 60000,
       });