Use modern for loops

Go 1.22 introduced a new [for-range](https://go.dev/ref/spec#For_range)
construct that looks a tad better than the usual `for i := 0; i < N; i++`
construct. I also tool the liberty of replacing some
`for i := 0; i < len(myitemsarray); i++ { … myitemsarray[i] …}`
with  `for item := range myitemsarray` when `myitemsarray` contains only pointers.

internal/cli/refresh_feeds.go

@@ -45,7 +45,7 @@ func refreshFeeds(store *storage.Storage) {
 		slog.Int("nb_workers", config.Opts.WorkerPoolSize()),
 	)
 
-	for i := 0; i < config.Opts.WorkerPoolSize(); i++ {
+	for i := range config.Opts.WorkerPoolSize() {
 		wg.Add(1)
 		go func(workerID int) {
 			defer wg.Done()