feat: flag accounts Reddit considers unestablished and re-test them

New accounts cannot start chats until Reddit considers them established.
Until now the bot would burn a candidate on every invitation Reddit was
always going to reject, with nothing in the dashboard explaining why the
account looked idle.

Two signals feed the verdict. A periodic profile check reads the
account's own age, karma and email verification from about.json and
compares them against configurable thresholds — that is what flags a
brand new account before it wastes anything. A rejected invitation is
authoritative: Reddit has told us directly, so the account is held out of
sending with a backoff that doubles per rejection, and a delivered
invitation clears the flag outright.

An unestablished account takes no new posts (canAcceptPost), raises an
attention item, reports an `unestablished` sending state, and shows its
age/karma evidence on the Accounts page. An unchecked account is always
allowed through, so a first run is never blocked.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/dashboard/src/features/overview/overview-page.tsx

@@ -89,6 +89,7 @@ const sendingStateCopy: Record<AccountStatus['sendingState'], { label: string; t
   'matrix-cooldown': { label: 'Matrix cooldown', tone: 'warning', detail: 'Only this account is paused by Reddit chat throttling.' },
   'replies-prioritized': { label: 'Replies first', tone: 'neutral', detail: 'Inbound replies are being handled before new outreach.' },
   pacing: { label: 'Pacing', tone: 'neutral', detail: 'Waiting for the account sending window.' },
+  unestablished: { label: 'Not established', tone: 'warning', detail: 'Reddit will not accept chat invitations from this account yet.' },
 };
 
 function AccountStatusPanel({ accounts }: { accounts: readonly AccountStatus[] }) {