Spork Android android-20260728203112

fix(admin): show a retry when deck, run, or draft reads fail (#31)

Manage Decks and Quiz Studio rendered a failed list read as a false empty —
"no decks yet" or silently-empty runs/drafts sections — with no way to recover.
Amplify's `.list()` resolves (never rejects) on GraphQL errors, so a transient
failure looked identical to genuinely empty. Same root cause as the play/
discover/flashcards fixes; last of the swallowed reads in the app.

- unwrap the reads in `fetchAllDecks`, `fetchGenerationRuns`, `fetchQuizRuns`,
  and `fetchDraftQuizzes` so a failure throws (→ react-query error).
- Route the deck list (ManageDecks) and the runs/drafts sections (QuizAdmin)
  through the shared `LoadState` (isError → retry). The generate/create forms
  above stay usable — only the list sections gate.
- Cover it: unit tests (each fetch throws on errors; each screen surfaces a
  retry that fires refetch, form still present) + Gherkin scenarios failing the
  specific read (listDecks; listGenerationRuns/listQuizzes).