fix(telegram): dedupe candidates before sending

Deduplicate candidates by aid at the notifier boundary so duplicate queue entries cannot produce repeated message bodies and button rows. The discovery layer already deduped by aid; this adds defense in depth with a regression test.

reaction_board/notify/telegram.py

@@ -98,7 +98,15 @@ class TelegramClient:
         return self._call("sendMessage", params)
 
     def send_candidates(self, candidates: Sequence[Mapping[str, Any]]) -> bool:
-        items = list(candidates)
+        # 通知器边界再做一次 aid 去重，避免调用方重复入队导致消息主体和按钮重复。
+        items: list[Mapping[str, Any]] = []
+        seen: set[int] = set()
+        for candidate in candidates:
+            aid = candidate.get("aid")
+            if aid in seen:
+                continue
+            seen.add(aid)
+            items.append(candidate)
         if not items:
             return True
         for index in range(0, len(items), MAX_CANDIDATES_PER_MESSAGE):