Report each symbol's next-leg stats to the master; drop per-symbol commission

- lib/leg-estimate: an account's next leg sized on every surveyed
  candidate (planLegSize, ranked by rankForTarget) — notional, its
  multiple of the account and the broker's maximum, expected hold, cost
  and win chance. The dashboard's hold estimate and the reporter share it.
- The reporter sends it per DXtrade firm as symbolStats, for one live
  account from the largest prefix group with a leg left to trade.
- The symbol map's per-symbol commission is gone: the firm's applies.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/page.tsx

@@ -396,8 +396,8 @@ function AccountRow({ account, firm, hideDead, privacy, onAssigned }: {
                             {account.holdEstimate && (
                                 <span
                                     className="text-slate-500"
-                                    title={`Next leg on ${account.holdEstimate.symbol}: $${Math.round(account.holdEstimate.notional).toLocaleString()} notional`
-                                        + (account.holdEstimate.leverage !== null ? ` (${account.holdEstimate.leverage}:1 max)` : '')
+                                    title={`Next leg on ${account.holdEstimate.symbol}: $${Math.round(account.holdEstimate.notional).toLocaleString()} notional, ${account.holdEstimate.multiplier}× the account`
+                                        + (account.holdEstimate.leverage !== null ? ` (${account.holdEstimate.leverage}× max)` : '')
                                         + ` at a measured volatility of ${(account.holdEstimate.volatilityPerDay * 100).toFixed(2)}%/day over the past week`
                                         + (account.holdEstimate.winProbability !== null ? `, wins ~${Math.round(account.holdEstimate.winProbability * 100)}% of the time` : '')
                                         + (account.holdEstimate.swapReserve > 0 ? `; its take-profit carries ~$${fmt(account.holdEstimate.swapReserve)} of expected swap` : '')