feat(dc): Add multi-metric transformation feature (direction 1+2)

Summary:
- Implement intelligent multi-metric grouping detection algorithm
- Add direction 1: timepoint-as-row, metric-as-column (analysis format)
- Add direction 2: timepoint-as-column, metric-as-row (display format)
- Fix column name pattern detection (FMA___ issue)
- Maintain original Record ID order in output
- Add full-select/clear buttons in UI
- Integrate into TransformDialog with Radio selection
- Update 3 documentation files

Technical Details:
- Python: detect_metric_groups(), apply_multi_metric_to_long(), apply_multi_metric_to_matrix()
- Backend: 3 new methods in QuickActionService
- Frontend: MultiMetricPanel.tsx (531 lines)
- Total: ~1460 lines of new code

Status: Fully tested and verified, ready for production

frontend-v2/src/modules/dc/pages/tool-c/index.tsx

@@ -16,7 +16,7 @@ import BinningDialog from './components/BinningDialog';
 import ConditionalDialog from './components/ConditionalDialog';
 import MissingValueDialog from './components/MissingValueDialog';
 import ComputeDialog from './components/ComputeDialog';
-import PivotDialog from './components/PivotDialog';
+import TransformDialog from './components/TransformDialog';
 import * as api from '../../api/toolC';
 
 // ==================== 类型定义 ====================
@@ -341,7 +341,7 @@ const ToolC = () => {
         onApply={handleQuickActionDataUpdate}
       />
 
-      <PivotDialog
+      <TransformDialog
         visible={state.pivotDialogVisible}
         columns={state.columns}
         sessionId={state.sessionId}