`apply_busy_delta` / `apply_event` not idempotent on restart replay

[wmagev]

If the validator crashes mid-block, the same block is reprocessed on restart (allways/validator/event_watcher.py:381-413).

insert_swap_outcome uses INSERT OR REPLACE (fine), but the busy-delta increments double — each replayed event bumps the counter again.

Direction: dedupe by (block, extrinsic_index, event_index), or store an absolute busy count instead of applying deltas.