feat: contract types for Post bookmarks (ApiPostBookmark*)

[arturasmckwcz]

Context

need4deed-org/be#929 needs a bookmark ("save for later") toggle on Posts for the Posts page rebuild (need4deed-org/fe#969 epic). Per shared-rules.md, the API contract must be defined here first.

Scope

• POST/DELETE bookmark request types (post id only — no request body needed beyond the route param)
• Add bookmarked: boolean (scoped to the requesting user) to ApiPostGet/ApiPostGetList
• Optional: a bookmarked query param type for ApiPostGetListParams to support a future "saved posts" view

Acceptance criteria

• Types added and exported from the SDK
• Version bumped and published to npmjs.com

Blocks: need4deed-org/be#929
Referenced from need4deed-org/fe#969