Enhance dashboard summary and statistics with new fields and caching improvements

- Added new field `Days` and `ScrapedTED` to `SummaryResponse` for tracking daily TED scrape counts.
- Updated `SummaryQuery` to include `Days` parameter for querying scraped TED data.
- Modified `Summary` handler to accept and process the new `Days` parameter.
- Refactored `Summary` method in the repository to support the new `Days` parameter and improved aggregation logic.
- Enhanced caching logic in the service layer to utilize a composite cache key based on `closingWindowSec` and `days`, improving cache management and retrieval efficiency.

This update improves the dashboard's functionality by providing more detailed insights into TED scraping activities and optimizing the caching strategy for better performance.

internal/dashboard/form.go

@@ -3,6 +3,7 @@ package dashboard
 // SummaryQuery binds query params for GET /dashboard/summary.
 type SummaryQuery struct {
 	ClosingWindow int `query:"closing_window"`
+	Days          int `query:"days"`
 }
 
 // TrendQuery binds query params for GET /dashboard/trend.