Drop the index hint from the auto-postpone sweep

[jorgemanrubia]

Removes the use_index pin from Card::Entropic.auto_postpone_all_due, keeping the (account_id, board_id, status) index added in #2970.

Once MySQL collected statistics on the new index, the planner started choosing it for the sweep on its own. The forced pin is no longer needed and is better left to the planner, which can adapt per-account as data shifts — a background sweep doesn't warrant a hardcoded plan.

The index stays; only the hint is removed.

[Copilot]

Pull request overview

Removes the forced MySQL optimizer index hint from the hourly card auto-postpone (entropy) sweep, relying on the optimizer to choose the appropriate plan now that statistics for the (account_id, board_id, status) index have stabilized. This keeps the underlying index (added in #2970) while reducing hardcoded query-plan coupling in background processing.

Changes:

• Removes the .use_index(:index_cards_on_account_id_and_board_id_and_status) hint from Card::Entropic.auto_postpone_all_due.
• Removes the now-obsolete explanatory comment describing why the hint was pinned.

Tip

If you aren't ready for review, convert to a draft PR.
Click "Convert to draft" or run gh pr ready --undo.
Click "Ready for review" or run gh pr ready to reengage.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.