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/accounts/accounts.css

@@ -8,3 +8,13 @@
 .account-row > div { display: grid; gap: .2rem; min-width: 0; }
 .account-row span { color: var(--muted); font-size: .82rem; }
 .account-row .pill { font-size: .7rem; }
+.account-row > .account-row-pills { display: flex; flex-wrap: wrap; align-items: center; gap: .4rem; }
+
+/* Establishment evidence sits on its own row beneath the account summary. */
+.account-establishment { flex-basis: 100%; display: grid; gap: .4rem; padding-top: .7rem; border-top: 1px solid var(--border); }
+.account-establishment .account-establishment-reason { margin: 0; font-size: .82rem; }
+.account-establishment .field-hint { margin: 0; }
+.account-establishment-metrics { display: flex; flex-wrap: wrap; gap: .35rem 1.25rem; margin: 0; }
+.account-establishment-metrics > div { display: grid; gap: .1rem; }
+.account-establishment-metrics dt { color: var(--muted); font-size: .7rem; text-transform: uppercase; letter-spacing: .04em; }
+.account-establishment-metrics dd { margin: 0; font-size: .82rem; font-variant-numeric: tabular-nums; }