feat: add header channel selector & adding channel modal menu

app/(dashboard)/external-channels/page.tsx

@@ -49,8 +49,10 @@ import {
 } from "@/components/ui/dialog";
 import { Label } from "@/components/ui/label";
 import { Textarea } from "@/components/ui/textarea";
+import { useTargetChannel } from "@/components/providers/target-channel-provider";
 
 export default function ExternalChannelsPage() {
+  const { selectedChannel } = useTargetChannel();
   const [channels, setChannels] = useState<ExternalChannel[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
@@ -68,23 +70,20 @@ export default function ExternalChannelsPage() {
   });
 
   useEffect(() => {
-    loadChannels();
-  }, []);
+    if (selectedChannel) {
+      loadChannels();
+    } else {
+      setLoading(false);
+    }
+  }, [selectedChannel]);
 
   const loadChannels = async () => {
+    if (!selectedChannel) return;
+
     try {
       setLoading(true);
-      // Сначала загружаем target channels
-      const targetChannelsRes = await channelsApi.list();
-      if (targetChannelsRes.target_channels.length === 0) {
-        setError("Добавьте сначала целевой канал");
-        setLoading(false);
-        return;
-      }
-
-      // Загружаем external channels для первого target channel
-      const firstTargetChannel = targetChannelsRes.target_channels[0];
-      const response = await externalChannelsApi.list(firstTargetChannel.id);
+      setError(null);
+      const response = await externalChannelsApi.list(selectedChannel.id);
       setChannels(response.external_channels);
     } catch (err: any) {
       const errorMsg =