feat(event): add single-thread event publisher with retry and cleanup

channel-service/app/repositories/event_store.py

@@ -96,6 +96,15 @@ class EventStore:
             attempt_count=row["attempt_count"],
         )
 
+    def get(self, event_id: str) -> Optional[OutboundEvent]:
+        row = self._connection().execute(
+            "SELECT id, event_type, payload, status, attempt_count FROM outbound_events WHERE id = ?",
+            (event_id,),
+        ).fetchone()
+        if row is None:
+            return None
+        return self._row_to_event(row)
+
     def mark_delivered(self, event_id: str) -> None:
         now = self._now().isoformat()
         with self._connection() as conn: