fix(history): show an error state instead of the empty "no attempts" message when loading fails

[nastaso]

Context

When a signed-in user opens Exam History and the exam_attempts fetch fails (a transient network or RLS error), loadHistory logs the error, leaves attempts as [], and clears loading. The render then shows the empty-state message "No exam attempts yet. Take your first practice exam!", so a returning user who actually has history is told they have none. The page cannot tell "no history" apart from "failed to load".

Scope

• File: src/pages/_History.tsx.
• loadHistory (around line 216): the catch (around line 233) currently only calls logError. Add an error state set there.
• Render (around line 542): when the new error state is set, show a distinct "Could not load your history. Retry." card with a retry button instead of the empty state. The empty state should only render after a successful load with genuinely zero attempts.
• Keep it minimal and in-file. Do not change the query, scoring, or any Supabase call shape.

Acceptance criteria

• A failed history load renders a clearly different "could not load / retry" UI, not the "no attempts yet" empty state.
• The empty state still shows for a real zero-attempt user.
• Retry re-runs loadHistory.
• npm run lint and npm run test pass; no new dependencies.

[tanishxdev]

i! I'd like to work on this issue. Could you please assign it to me?

[nastaso]

Resolved by #145: _History.tsx now holds a loadError state and renders a "Try again" retry card on a failed load, so the empty "no attempts" message only shows when there genuinely are none. Closing as done.