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/migrations.py

@@ -174,6 +174,18 @@ MIGRATIONS: tuple[Migration, ...] = (
             "ALTER TABLE folder_resource ADD COLUMN fav_time INTEGER",
         ),
     ),
+    Migration(
+        version=3,
+        name="candidate stats",
+        statements=(
+            "ALTER TABLE candidate ADD COLUMN duration INTEGER",
+            "ALTER TABLE candidate ADD COLUMN play INTEGER",
+            "ALTER TABLE candidate ADD COLUMN like INTEGER",
+            "ALTER TABLE candidate ADD COLUMN favorite INTEGER",
+            "ALTER TABLE candidate ADD COLUMN danmaku INTEGER",
+            "ALTER TABLE candidate ADD COLUMN review INTEGER",
+        ),
+    ),
 )