feat(p3): add discovery, telegram notifications, and one-click favorites

Implement WBI video search with legacy fallback, classification scoring, candidate pool, permanent seen-aid dedupe, blacklist filtering, and batched Telegram notifications. Add write client for fav deal/sort, target-folder selection, insertion position calculation, read-back verification, fav_action locking, retry on failure, ignore and blacklist actions. Wire discovery, candidate cleanup, Telegram long polling, and new discover/candidates CLI commands into the scheduler. Add migration v3 for candidate duration and index stats.

reaction_board/services/folder_sync.py

@@ -260,6 +260,9 @@ class FolderSyncService:
                 outcome = self.repo.upsert_from_fav(
                     resource, folder.media_id, was_added=aid in added, now=now
                 )
+                if aid in added:
+                    # 人工已加入收藏夹：候选池不再保留同一条视频
+                    self.repo.delete_candidate(aid)
                 if outcome.moved_folder:
                     self._log(
                         "warning",