[WEB-6420] chore: migrate community references from Discord to Forum (#8657)

* chore: replace Discord references with Forum links

* chore: migrate help and community CTAs from Discord to Forum

* refactor: replace Discord icons with lucide MessageSquare

* chore: rename Discord labels and keys to Forum

* chore: remove obsolete Discord icon component

* chore: update Discord references to Forum in templates

* chore: code refactoring

apps/web/app/(all)/workspace-invitations/page.tsx

@@ -115,7 +115,7 @@ function WorkspaceInvitationPage() {
               <EmptySpaceItem
                 Icon={Share2}
                 title="Join our community of active creators"
-                href="https://discord.com/invite/A92xrEGCge"
+                href="https://forum.plane.so"
               />
             </EmptySpace>
           )