Add archive project button and filter archived projects from selectors

- Add "Archive project" / "Unarchive project" button in the project
  configuration danger zone (ProjectProperties)
- Filter archived projects from the Projects listing page
- Filter archived projects from NewIssueDialog project selector
- Filter archived projects from IssueProperties project picker
  (keeps current project visible even if archived)
- Filter archived projects from CommandPalette
- SidebarProjects already filters archived projects

Co-Authored-By: Paperclip <noreply@paperclip.ing>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/NewIssueDialog.tsx

@@ -288,8 +288,12 @@ export function NewIssueDialog() {
     queryFn: () => authApi.getSession(),
   });
   const currentUserId = session?.user?.id ?? session?.session?.userId ?? null;
+  const activeProjects = useMemo(
+    () => (projects ?? []).filter((p) => !p.archivedAt),
+    [projects],
+  );
   const { orderedProjects } = useProjectOrder({
-    projects: projects ?? [],
+    projects: activeProjects,
     companyId: effectiveCompanyId,
     userId: currentUserId,
   });