Send cronjob result and notify-agent reaction to Telegram

The cronjob notification ran the notify-agent on the result summary and
sent only its reaction to Telegram. When the agent merely acknowledged the
summary (e.g. "👍"), the actual cronjob result never reached Telegram —
the user got a header plus an emoji and no information.

Send the real result as the guaranteed first Telegram message, then run
the notify-agent best-effort and send its reaction as a separate second
message. The agent run is wrapped in try/catch with a canRunNotifyAgent
guard instead of the old return-aborts, so a missing key / OpenAI without
key / unavailable CLI only skips the reaction — the result is already
delivered. The notify-agent still persists its reaction to the web history
automatically (ChatNonStreaming / ChatNonStreamingViaCli).

TelegramService.SendNotification now uses SendLongMessage so long results
are chunked into 4096-char messages instead of being rejected whole.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Services/TelegramService.cs

@@ -280,7 +280,10 @@ public class TelegramService
         if (bot == null || string.IsNullOrEmpty(bot.BotToken)) return;
 
         var chatId = long.Parse(session.TelegramChatId);
-        await SendMessage(chatId, bot.BotToken, text);
+        // SendLongMessage statt SendMessage: lange Ergebnisse (z.B. Cronjob-Antworten) werden in
+        // 4096-Zeichen-Chunks zerlegt. Sonst lehnt die Telegram-API zu lange Texte komplett ab
+        // (400 → der User bekäme gar nichts).
+        await SendLongMessage(chatId, bot.BotToken, text);
     }
 
     // ── Telegram Bot API ──