Auto-claim without the scheduler, and no claim twice

A payout locks in profit and opens nothing, so stopping the trading no
longer stops it: a claim watcher runs the same claims once a minute while
the scheduler is off (its tick still claims while it runs), and the
dashboard's Auto-claim payouts box turns them off.

From two independent reviews of the claim path:
- A claim holds every further claim on the account until Vest's
  transactions show its WITHDRAW. A sync already out when the claim lands
  (by sync generation, not the clock) no longer writes the pre-claim
  balance back, and a fresh sync follows the claim.
- A withdraw that fails in transit (timeout, reset, 5xx) may have gone in:
  it is recorded as of unknown outcome and holds claims the same way,
  until the transactions show it, or an hour of them shows it didn't.
- claimProfit checks Vest's own account: funded (or instant), and no more
  than the balance above its starting capital.
- A claiming account is marked in flight; runClaims sends the amount it
  re-checked under the mutex.
- The watcher starts before the rest of the init can fail; settings are
  validated before any is written.

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

lib/platform-client.ts

@@ -139,6 +139,9 @@ export interface PlatformClient {
      *  Resolves once the platform accepted it and the books were updated;
      *  rejects with the platform's reason otherwise. */
     claimProfit?(accountId: number, amount: number): Promise<{ claimed: number; received: number | null }>;
+    /** A claim this client made that no good sync has read past yet: the
+     *  balance on hand may not show it, so no claim may be judged on it. */
+    claimPending?(accountId: number): boolean;
     /** Drop the account's history from memory (the wipe routes), so it reads
      *  unloaded until the next fetch rebuilds it. */
     forgetHistory(accountId: number, accountName: string): void;