Add frontend elements to enable sorting by pinned/unpinned and buttons for pinning/unpinning and pin icons on pinned posts.

[lhitmi]

This issue addresses the pin announcements user story and is scheduled for completion in Sprint 1, with high impact and moderate effort. It involves adding front-end functionality to display pin/unpin buttons, show pin icons on pinned posts, and enable sorting by pinned/unpinned status, ensuring all features work seamlessly for users and admins. User story is issue #16

[mohamed-elzeni]

This is cancelled since it's already implemented in NodeBB.