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>

tests/database.test.ts

@@ -107,7 +107,7 @@ describe('Database Client', () => {
         .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%'")
         .all() as { name: string }[];
       // Existing domain/config tables plus account, conversation, sync and media ownership stores.
-      expect(tables.length).toBe(22);
+      expect(tables.length).toBe(23);
       expect(tables.map((table) => table.name)).toEqual(expect.arrayContaining([
         'candidate_queue',
         'runtime_state',
@@ -115,6 +115,7 @@ describe('Database Client', () => {
         'media_library_sends',
         'conversation_read_state',
         'reddit_recipient_account_status',
+        'reddit_account_establishment',
       ]));
     });