Reduce slow query threshold from 50ms to 25ms

This will help identify performance issues earlier by logging
any database query that takes longer than 25 milliseconds.

internal/database/slowquery.go

@@ -8,7 +8,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 )
 
-const slowQueryThreshold = 50 * time.Millisecond
+const slowQueryThreshold = 25 * time.Millisecond
 
 // logSlowQuery logs queries that take longer than slowQueryThreshold
 func logSlowQuery(logger *logger.Logger, query string, start time.Time) {