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.

tests/test_folder_sync.py

@@ -143,11 +143,19 @@ def test_initial_import_and_incremental_skip():
         clock = [1_800_000_000]
         db, repo, service = make_service(tmp, transport, clock)
         try:
+            repo.upsert_candidate(
+                aid=1101, bvid="BV1101", title="咻咻满 reaction",
+                up_mid=100, up_name="UP", pubdate=1_799_000_000,
+                cover=None, score=3, channel="search:test#p1",
+                now=1_799_999_000,
+            )
             summary = service.run()
             assert summary.ok
             assert summary.added == 4
             assert summary.missing == 1
             assert summary.refreshed == 3
+            # 人工加入收藏夹后，同 aid 候选自动移除
+            assert repo.get_candidate(1101) is None
             assert repo.seed_blacklist([999], now=0) == 0  # 已由 service 写入
 
             assert repo.get_video(1101)["status"] == "active"