latest changes about putting it on the last and more

v3.2.0: 3-tier smart column matching, append-at-end, bug fixes

Major Features:
- 3-tier smart column matching (exact → contains → skip)
  Reads Row 1 headers and maps data to correct columns regardless of
  column order, naming, or extra columns (Type, Colour, etc.)
- Append at true end: new rows always go after the last row with data
  across ALL columns, never in gaps or at the top
- Smart batchUpdate: only writes to plugin-managed cells, leaves all
  other columns completely untouched
- SEO Title restored as a matchable data field

Bug Fixes:
- get_values() now propagates WP_Error instead of swallowing it
- Post ID validation order fixed (checked before current_user_can)
- find_row_by_post_id() now returns WP_Error on API failures
- Removed /X/g regex that corrupted tag names containing letter X
- Replaced deprecated current_time('timestamp') with time()
- Fixed cache duration comment (said 12h, was actually 6h)