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.

config.example.json

@@ -60,12 +60,18 @@
     "snapshot_at": "00:01",
     "candidate_ttl_days": 7
   },
+  "discover": {
+    "keywords": ["咻咻满 reaction", "咻咻满 充电"],
+    "pages": 2,
+    "window_days": 14
+  },
   "notify": {
     "min_score": 2,
     "max_items_per_message": 10
   },
   "classify": {
     "require_title": "咻咻满",
+    "self_mid": 37754047,
     "positive": [
       "reaction",
       "re",