feat(talk): add getRecentMessagesV2 for single-call recent-message fetch

[enkunkun]

Description

Adds TalkService.getRecentMessagesV2({messageBoxId, messagesCount}) — the
direct LINE-server API for "give me the last N messages in this box". CHRLINE
has exposed this since forever and the server still honors it; the struct is
also already declared in resources/line/chrline.thrift in this repo, just
never wired through to the runtime.

Today's LINEJS forces callers to first call getMessageBoxes, dig out
lastDeliveredMessageId, and then call getPreviousMessagesV2WithRequest
just to fetch the most recent N messages (this is what Chat.fetchMessages
does internally). That extra round-trip is unnecessary for polling loops,
initial-fetch tools, or anywhere the caller only cares about "the latest".

Wire format (fid 2 string messageBoxId, fid 3 i32 messagesCount,
result list<Message> at fid 0) is verified against a live LINE account:
returns Message objects with the same shape as getPreviousMessagesV2WithRequest.

What changed

• packages/types/thrift.ts — added getRecentMessagesV2_args and
  _result entries alongside getPreviousMessagesV2WithRequest_result.
• packages/types/line_types.ts — matching TypeScript interfaces.
• packages/linejs/base/thrift/readwrite/struct.ts — args factory,
  placed next to getPreviousMessagesV2WithRequest_args.
• packages/linejs/base/service/talk/mod.ts — async getRecentMessagesV2
  method following the same client.request.request(...) pattern used by
  every other method on the service.

Usage:

const messages = await client.base.talk.getRecentMessagesV2({
  messageBoxId: "u...",
  messagesCount: 100,
});

Checklist

• Verified against live LINE (returns Message[] matching
  getPreviousMessagesV2WithRequest shape)
• Follows existing TalkService method pattern (LINEStruct factory +
  client.request.request)
• No new tests — the method is a thin wrapper over an existing pattern
  and would only test the wire encoding

[EdamAme-x]

LGTME!