feat(fusion_accounting_bank_rec): pre-aggregated MV for OWL widget perf

CREATE MATERIALIZED VIEW fusion_unreconciled_bank_line_mv pre-computes
the data the kanban widget needs (top suggestion, confidence band,
attachment count, partner reconcile hint) so that listing 50-100 lines
is one indexed query instead of N+1.

Refresh strategy:
- Triggered on fusion.reconcile.suggestion create/write (best-effort,
  never poisons the originating transaction)
- Cron (every 5 min) — added in Task 25

The MV is created in the model's init() (Odoo calls this on
install/upgrade). The SQL DDL is idempotent
(CREATE MATERIALIZED VIEW IF NOT EXISTS / CREATE INDEX IF NOT EXISTS)
and includes a UNIQUE(id) index so REFRESH MATERIALIZED VIEW
CONCURRENTLY is supported. _refresh() falls back to a blocking refresh
on the first call after creation.

Made-with: Cursor

fusion_accounting_bank_rec/models/__init__.py

@@ -5,3 +5,4 @@ from . import fusion_bank_rec_widget
 from . import account_bank_statement_line
 from . import account_reconcile_model
 from . import fusion_reconcile_engine
+from . import fusion_unreconciled_bank_line_mv