refactor(frontend): extract logic to hooks, split inline components

Area 1 (tv/page.tsx 964→423 lines):
- hooks: use-fullscreen, use-idle, use-volume, use-quality, use-subtitles,
  use-channel-input, use-channel-passwords, use-tv-keyboard
- components: SubtitlePicker, VolumeControl, QualityPicker, TopControlBar,
  LogoWatermark, AutoplayPrompt, ChannelNumberOverlay, TvBaseLayer

Area 2 (edit-channel-sheet.tsx 1244→678 lines):
- hooks: use-channel-form (all form state + reset logic)
- lib/schemas.ts: extracted Zod schemas + extractErrors
- components: AlgorithmicFilterEditor, RecyclePolicyEditor, WebhookEditor,
  AccessSettingsEditor, LogoEditor

Area 3 (dashboard/page.tsx 406→261 lines):
- hooks: use-channel-order, use-import-channel, use-regenerate-all
- lib/channel-export.ts: pure export utility
- components: DashboardHeader

k-tv-frontend/hooks/use-import-channel.ts

@@ -0,0 +1,47 @@
+"use client";
+
+import { useState } from "react";
+import { useQueryClient } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { ChannelImportData } from "@/app/(main)/dashboard/components/import-channel-dialog";
+
+export function useImportChannel(token: string | null) {
+  const queryClient = useQueryClient();
+  const [isPending, setIsPending] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  const handleImport = async (data: ChannelImportData) => {
+    if (!token) return;
+    setIsPending(true);
+    setError(null);
+    try {
+      const created = await api.channels.create(
+        {
+          name: data.name,
+          timezone: data.timezone,
+          description: data.description,
+        },
+        token,
+      );
+      await api.channels.update(
+        created.id,
+        {
+          schedule_config: { blocks: data.blocks },
+          recycle_policy: data.recycle_policy,
+        },
+        token,
+      );
+      await queryClient.invalidateQueries({ queryKey: ["channels"] });
+      return true; // success signal for closing dialog
+    } catch (e) {
+      setError(e instanceof Error ? e.message : "Import failed");
+      return false;
+    } finally {
+      setIsPending(false);
+    }
+  };
+
+  const clearError = () => setError(null);
+
+  return { handleImport, isPending, error, clearError };
+}