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>

README.md

@@ -257,7 +257,11 @@ own traffic since Vest publishes no API):
   unmarked since marking began was someone else's. The **Trades** button on
   the Vest firm's dashboard row lists them, and the account page shows its own.
 - Claims: the bot claims a funded account's profit by itself at each stage's
-  target (`auto_claim`, on unless set to `off`). The account page's **Claim
+  target — whether or not the scheduler is running (a claim opens nothing).
+  The dashboard's **Auto-claim payouts** box turns it off (`auto_claim`). A
+  claim holds every further claim on the account until Vest's transactions
+  show its WITHDRAW; one whose request failed in transit holds them too, until
+  the transactions show it went in, or an hour of them shows it didn't. The account page's **Claim
   now** button claims the whole profit above the account size at once — any
   amount from $1 — when the account is flat; it asks first, since it moves
   money to the login's main account.