Fix sort order after column reorder on page reload

[wschopohl]

Summary

• Fixes incorrect sort order when columns have been reordered via colReorder drag-and-drop and the page is reloaded
• The saved sort state uses visual (post-reorder) column indices, but initial_order was sending them to the server as-is — the server interpreted them as original indices, sorting the wrong column
• Uses the saved colReorder mapping to translate visual indices back to original indices before sending initial_order in the _init request

Steps to reproduce

1. Open any DataTables view (e.g. parts list)
2. Drag a column to reorder it
3. Click a column header to sort
4. Reload the page
5. Before fix: wrong column is sorted. After fix: correct column is sorted.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.20%. Comparing base (a82d515) to head (31e3049).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1346      +/-   ##
============================================
- Coverage     57.22%   57.20%   -0.03%     
  Complexity     8410     8410              
============================================
  Files           616      616              
  Lines         27117    27117              
============================================
- Hits          15518    15512       -6     
- Misses        11599    11605       +6     

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