- Adds a new `MercadosFeriados` table to the database to persist market holidays.
- Implements `HolidayDataFetcher` to update holidays weekly from Finnhub API.
- Implements `IHolidayService` with in-memory caching to check for holidays efficiently.
- Worker service now skips fetcher execution on market holidays.
- Adds a new API endpoint `/api/mercados/es-feriado/{mercado}`.
- Integrates a non-blocking holiday alert into the `BolsaLocalWidget`."
