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>

src/config/index.ts

@@ -164,6 +164,36 @@ export const ConfigSchema = z.object({
     killOnSellerKeyword: true,
     aiReplyScreening: { enabled: false, killConfidence: 0.8, flagConfidence: 0.6 },
   }),
+  /**
+   * New Reddit accounts cannot start chats until Reddit considers them
+   * established. Rather than burning candidates on invitations Reddit will
+   * reject, an account is flagged and held out of outbound sending, then
+   * re-tested on an interval.
+   */
+  accountEstablishment: z.object({
+    enabled: z.boolean().default(true),
+    /** How often an account's own age/karma profile is refreshed. */
+    profileCheckIntervalMs: z.number().int().min(60_000).default(6 * 60 * 60_000),
+    minAccountAgeDays: z.number().min(0).default(7),
+    minTotalKarma: z.number().int().min(0).default(20),
+    minCommentKarma: z.number().int().min(0).default(5),
+    requireVerifiedEmail: z.boolean().default(false),
+    /**
+     * How long to hold an account out of sending after Reddit rejects an
+     * invitation for being too new. Doubles per consecutive rejection.
+     */
+    probeRetryBaseMs: z.number().int().min(60_000).default(4 * 60 * 60_000),
+    probeRetryMaxMs: z.number().int().min(60_000).default(48 * 60 * 60_000),
+  }).default({
+    enabled: true,
+    profileCheckIntervalMs: 6 * 60 * 60_000,
+    minAccountAgeDays: 7,
+    minTotalKarma: 20,
+    minCommentKarma: 5,
+    requireVerifiedEmail: false,
+    probeRetryBaseMs: 4 * 60 * 60_000,
+    probeRetryMaxMs: 48 * 60 * 60_000,
+  }),
   pushNotifications: z.object({
     enabled: z.boolean().default(false),
     /** Base URL of the ntfy server, e.g. https://ntfy.example.com. */