fix(fe): KsDataGrid - prevent duplicate edit mode on cell focus

Improved onCellFocused to check if already editing same cell before starting edit mode.

Problem: Enter key moves to next cell + startEditingCell(), then onCellFocused fires
and tries to startEditingCell() again on same cell, causing timing issues.

Solution: Check getEditingCell() to see if we're already editing the focused cell
- If same cell: skip (already editing)
- If different cell: enter edit mode

Result: Enter key → next cell → auto edit mode (no duplication)
Tab/Click/Arrow → auto edit mode (only once)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/shared/ui/components/KsDataGrid.vue

@@ -117,12 +117,19 @@ function onCellFocused(event: CellFocusedEvent): void {
   if (event.column && event.rowIndex !== undefined) {
     const colDef = event.column.getColDef()
     if (colDef.editable) {
-      setTimeout(() => {
+      const currentEditingCell = event.api.getEditingCell()
+      const focusedColId = event.column.getColId()
+
+      const isSameCell = currentEditingCell &&
+        currentEditingCell.rowIndex === event.rowIndex &&
+        currentEditingCell.column?.getColId() === focusedColId
+
+      if (!isSameCell) {
         event.api.startEditingCell({
           rowIndex: event.rowIndex,
-          colKey: event.column!.getColId()
+          colKey: focusedColId
         })
-      }, 50)
+      }
     }
   }
 }