[simplex]: show the BRIDGE balance as soon as a top-up is delivered

[seunlanlege]

The dashboard's BRIDGE balance stayed stale for up to a minute after a top-up completed.

Why: the Hyperbridge balance is not part of BalanceProvider.refresh(). trackHyperbridgeBalance reads it once at boot and then on the same once-a-minute interval as the EVM chains, because the substrate read is cheap to cache and rarely urgent. When a top-up flips to delivered, the UI reloads balances immediately (OperatorOverview calls onBalancesChanged on the delivered transition, and GET /api/balances?refresh=1 re-reads the EVM chains) — but the snapshot's hyperbridge field was whatever the last interval tick had read.

Fix:

• BalanceProvider.refreshHyperbridgeBalance() — the interval's read, now public and safe to call any time. No-op until tracking is initialized; a failed read keeps the last snapshot.
• BridgeTopUp takes an optional refreshBridgeBalance dep, called — best-effort and awaited — in readDelivery where the record transitions to delivered. Awaited inside the sync is what makes the dashboard's follow-up /api/balances read fresh rather than racing a fire-and-forget refresh.
• Wired in boot.ts to the balance provider.

Validation

• bridge-top-up suite: 14 passed, including a new assertion that the balance refresh fires exactly once on delivery.
• balance-provider suite: 12 passed.
• Biome: clean on changed files.
• tsc shows only the pre-existing errors on main (verified by stashing).