refactor(channels): consolidate media handling and improve resource cleanup

Extract common file download and audio detection logic to utils package,
implement consistent temp file cleanup with defer, add allowlist checks
before downloading attachments, and improve context management across
Discord, Slack, and Telegram channels. Replace logging with structured
logger and prevent context leaks in transcription and thinking animations.

pkg/channels/dingtalk.go

@@ -6,13 +6,13 @@ package channels
 import (
 	"context"
 	"fmt"
-	"log"
 	"sync"
 
 	"github.com/open-dingtalk/dingtalk-stream-sdk-go/chatbot"
 	"github.com/open-dingtalk/dingtalk-stream-sdk-go/client"
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/logger"
 	"github.com/sipeed/picoclaw/pkg/utils"
 )
 
@@ -48,7 +48,7 @@ func NewDingTalkChannel(cfg config.DingTalkConfig, messageBus *bus.MessageBus) (
 
 // Start initializes the DingTalk channel with Stream Mode
 func (c *DingTalkChannel) Start(ctx context.Context) error {
-	log.Printf("Starting DingTalk channel (Stream Mode)...")
+	logger.InfoC("dingtalk", "Starting DingTalk channel (Stream Mode)...")
 
 	c.ctx, c.cancel = context.WithCancel(ctx)
 
@@ -70,13 +70,13 @@ func (c *DingTalkChannel) Start(ctx context.Context) error {
 	}
 
 	c.setRunning(true)
-	log.Println("DingTalk channel started (Stream Mode)")
+	logger.InfoC("dingtalk", "DingTalk channel started (Stream Mode)")
 	return nil
 }
 
 // Stop gracefully stops the DingTalk channel
 func (c *DingTalkChannel) Stop(ctx context.Context) error {
-	log.Println("Stopping DingTalk channel...")
+	logger.InfoC("dingtalk", "Stopping DingTalk channel...")
 
 	if c.cancel != nil {
 		c.cancel()
@@ -87,7 +87,7 @@ func (c *DingTalkChannel) Stop(ctx context.Context) error {
 	}
 
 	c.setRunning(false)
-	log.Println("DingTalk channel stopped")
+	logger.InfoC("dingtalk", "DingTalk channel stopped")
 	return nil
 }
 
@@ -108,10 +108,13 @@ func (c *DingTalkChannel) Send(ctx context.Context, msg bus.OutboundMessage) err
 		return fmt.Errorf("invalid session_webhook type for chat %s", msg.ChatID)
 	}
 
-	log.Printf("DingTalk message to %s: %s", msg.ChatID, utils.Truncate(msg.Content, 100))
+	logger.DebugCF("dingtalk", "Sending message", map[string]interface{}{
+		"chat_id":  msg.ChatID,
+		"preview":  utils.Truncate(msg.Content, 100),
+	})
 
 	// Use the session webhook to send the reply
-	return c.SendDirectReply(sessionWebhook, msg.Content)
+	return c.SendDirectReply(ctx, sessionWebhook, msg.Content)
 }
 
 // onChatBotMessageReceived implements the IChatBotMessageHandler function signature
@@ -152,7 +155,11 @@ func (c *DingTalkChannel) onChatBotMessageReceived(ctx context.Context, data *ch
 		"session_webhook":   data.SessionWebhook,
 	}
 
-	log.Printf("DingTalk message from %s (%s): %s", senderNick, senderID, utils.Truncate(content, 50))
+	logger.DebugCF("dingtalk", "Received message", map[string]interface{}{
+		"sender_nick": senderNick,
+		"sender_id":   senderID,
+		"preview":     utils.Truncate(content, 50),
+	})
 
 	// Handle the message through the base channel
 	c.HandleMessage(senderID, chatID, content, nil, metadata)
@@ -163,7 +170,7 @@ func (c *DingTalkChannel) onChatBotMessageReceived(ctx context.Context, data *ch
 }
 
 // SendDirectReply sends a direct reply using the session webhook
-func (c *DingTalkChannel) SendDirectReply(sessionWebhook, content string) error {
+func (c *DingTalkChannel) SendDirectReply(ctx context.Context, sessionWebhook, content string) error {
 	replier := chatbot.NewChatbotReplier()
 
 	// Convert string content to []byte for the API
@@ -172,7 +179,7 @@ func (c *DingTalkChannel) SendDirectReply(sessionWebhook, content string) error
 
 	// Send markdown formatted reply
 	err := replier.SimpleReplyMarkdown(
-		context.Background(),
+		ctx,
 		sessionWebhook,
 		titleBytes,
 		contentBytes,