fix: Add keyboard accessibility for table column and row reordering

[fkwq34]

fixes: #19605

Description
This PR adds keyboard support for reordering table columns and rows, addressing the WCAG accessibility requirement that drag-only functionality must have a keyboard alternative.

Changes

ReorderableColumn directive:

• Added Ctrl+Left / Ctrl+Right, Cmd+Left / Cmd+Right keyboard shortcuts to move columns
• Added ARIA attributes (tabindex, [aria-grabbed], [aria-label])
• Added screen reader announcements for column reorder operations

ReorderableRow directive:

• Added Ctrl+Up / Ctrl+Down, Cmd+Up / Cmd+Down keyboard shortcuts to move rows
• Added ARIA attributes (tabindex, [aria-grabbed], [aria-label])
• Added screen reader announcements for row reorder operations
• Focus correctly follows the moved row after reorder

Table component:

• Added moveColumnByKeyboard() and moveRowByKeyboard() methods
• Added focusColumnByIndex() and focusRowByIndex() helper methods
• Added _pendingRowFocusIndex for reliable focus management during Angular change detection

Accessibility

• Keyboard-only users can now reorder columns and rows without a mouse
• Screen readers announce position changes (e.g., "Row moved up from position 3 to position 2")
• Live region uses [aria-live="polite"] to avoid interrupting user flow
• Focus remains on the moved element, allowing consecutive keyboard operations

Testing

• Column reorder: Focus a column header, press Ctrl+Left / Ctrl+Right or Cmd+Left / Cmd+Right
• Row reorder: Focus a row with [pReorderableRow], press Ctrl+Up / Ctrl+Down or Cmd+Up / Cmd+Down
• Verified with keyboard-only navigation
• Verified screen reader announcements