Fix grain price fetcher

src/Managing.Application.Abstractions/Grains/IPriceFetcher15MinGrain.cs

@@ -7,7 +7,7 @@ namespace Managing.Application.Abstractions.Grains;
 /// This stateless worker grain handles fetching 5-minute price data from external APIs 
 /// and publishing to Orleans streams.
 /// </summary>
-public partial interface IPriceFetcher5MinGrain : IGrainWithIntegerKey
+public partial interface IPriceFetcher15MinGrain : IGrainWithIntegerKey
 {
     /// <summary>
     /// Fetches 5-minute price data for all supported exchange/ticker combinations