[BUG] Writer and Reader dashboards missing error state rendering

[realproject7]

Problem

PR #62 (Writer Dashboard) and PR #63 (Reader Dashboard) use React Query but never render the error state. If the Supabase query fails (network error, RLS denial, etc.), the user sees no feedback — stuck on empty state with no indication of failure.

Fix

• Both dashboards: render error state from useQuery with a user-visible error message
• Example: "Failed to load storylines. Please try again."
• npm run lint and npm run typecheck pass