fix golint errors

internal/telegram/bot.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
+	"strconv"
 	"strings"
 	"time"
 
@@ -93,8 +94,12 @@ func (b *Bot) nextSendTime() time.Time {
 	hour := 9
 	minute := 0
 	if len(parts) == 2 {
-		fmt.Sscanf(parts[0], "%d", &hour)
-		fmt.Sscanf(parts[1], "%d", &minute)
+		if h, err := strconv.Atoi(parts[0]); err == nil {
+			hour = h
+		}
+		if m, err := strconv.Atoi(parts[1]); err == nil {
+			minute = m
+		}
 	}
 
 	target := time.Date(now.Year(), now.Month(), now.Day(), hour, minute, 0, 0, b.loc)
@@ -185,7 +190,7 @@ type imageFile struct {
 
 // downloadImages downloads image attachments, skipping failures.
 func (b *Bot) downloadImages(ctx context.Context, attachments []memos.Attachment) []imageFile {
-	var files []imageFile
+	files := make([]imageFile, 0, len(attachments))
 	for _, att := range attachments {
 		data, err := b.client.DownloadAttachment(ctx, att)
 		if err != nil {