History Polling: Message-ID-basiert, neuer /api/history/poll Endpoint

Services/DatabaseService.cs

@@ -135,4 +135,13 @@ public class DatabaseService
             "SELECT * FROM messages WHERE chain_id = @chainId ORDER BY id", new { chainId }
         );
     }
+
+    public async Task<IEnumerable<MessageRecord>> GetMessagesAfterId(long afterId, int limit = 200)
+    {
+        using var conn = CreateConnection();
+        return await conn.QueryAsync<MessageRecord>(
+            "SELECT * FROM messages WHERE id > @afterId ORDER BY id LIMIT @limit",
+            new { afterId, limit }
+        );
+    }
 }