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/IssueProperties.tsx

@@ -131,8 +131,12 @@ export function IssueProperties({ issue, onUpdate, inline }: IssuePropertiesProp
     queryFn: () => projectsApi.list(companyId!),
     enabled: !!companyId,
   });
+  const activeProjects = useMemo(
+    () => (projects ?? []).filter((p) => !p.archivedAt || p.id === issue.projectId),
+    [projects, issue.projectId],
+  );
   const { orderedProjects } = useProjectOrder({
-    projects: projects ?? [],
+    projects: activeProjects,
     companyId,
     userId: currentUserId,
   });