feat(channels): wire contact auto-collector across all channel handlers

Pass contactCollector through channel manager to all channel handlers
(Telegram, Discord, Feishu, Slack, Zalo) so contacts are automatically
collected when users interact with the agent.

internal/channels/feishu/bot.go

@@ -85,6 +85,11 @@ func (c *Channel) handleMessageEvent(ctx context.Context, event *MessageEvent) {
 				MessageID: messageID,
 			}, c.historyLimit)
 
+			// Collect contact even when bot is not mentioned (cache prevents DB spam).
+			if cc := c.ContactCollector(); cc != nil {
+				cc.EnsureContact(ctx, c.Type(), c.Name(), mc.SenderID, mc.SenderID, senderName, "", "group")
+			}
+
 			slog.Debug("feishu group message recorded (no mention)",
 				"chat_id", mc.ChatID, "sender", senderName,
 			)