feat: recover missing conversations, fix media attachment, add manual inbox tab

Missing conversations: recipient Reddit accounts that are deleted or suspended
left conversations unaccounted for. A new RecipientAccountStatusService polls
Reddit for the users behind cached conversations and records their account
status durably, with progressive backfill and delta-media fixes in ChatService
so history and images are no longer dropped mid-sync.

Media: attachMedia now surfaces download failures as MediaAttachmentError so the
sync cursor can be retried instead of silently losing an image, recognizes image
bytes when Matrix returns a generic content type, and keeps separate gallery
occurrences when the same asset appears in more than one event.

Manual inbox tab: the conversations list now carries the reply-loop status, so
the inbox can separate conversations the operator is driving by hand from the
ones automation is still handling. A Manual filter pill and a per-row chip
explain why each conversation was handed over.

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

tests/chat-service-auth-gate.test.ts

@@ -75,7 +75,7 @@ describe('ChatService account authentication gate', () => {
     await vi.waitFor(() => expect(matrix.sync).toHaveBeenCalledOnce());
     finishSync({ next_batch: 's1' });
 
-    await expect(Promise.all([first, second])).resolves.toEqual([undefined, undefined]);
+    await expect(Promise.all([first, second])).resolves.toEqual([0, 0]);
     expect(matrix.sync).toHaveBeenCalledOnce();
   });