[nitonitori]

Add playlist id:<ID> and 歌单 id:<ID> so a known Netease playlist can be added to the TeamSpeak queue without searching first. Direct IDs share the existing playlist loader, enqueue and idle-start path used by select.

Positive ASCII decimal IDs are accepted; malformed/zero IDs are rejected before an API request. Bare numeric arguments remain keyword searches, and direct import preserves the user's previous search cache. Chinese and English usage documentation and in-chat help are updated.

Validation:

• Watched the direct-ID tests fail before implementation.
• Linux/Python3.11 complete backend regression suite: 78 tests passed.
• New tests use a real temporary SQLite queue and cover direct import, Chinese alias, case/leading zeroes, malformed IDs, numeric keyword compatibility, preserved search selection and empty playlists.
• No web, voice protocol or dependency changes. No real playlist was inserted into a live channel during validation.

Closes #21