- Replace synthetic fallback in getQuote()/getPriceHistory() with null returns
- Add QuoteResult/PriceHistoryResult types with { value, stale } structure
- Implement stale-while-revalidate: return cached value with stale=true on live fetch failure
- Cache failures for 30s to avoid hammering provider
- Update CompanyAnalysis type to use PriceData<T> wrapper
- Update task-processors to track failed/stale tickers explicitly
- Update price-history-card UI to show unavailable state and stale indicator
- Add comprehensive tests for failure cases
- Add e2e tests for null data, stale data, and live data scenarios
Resolves#14
