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-idle.ts

@@ -0,0 +1,38 @@
+"use client";
+
+import { useState, useEffect, useCallback, useRef, RefObject } from "react";
+
+export function useIdle(
+  timeoutMs: number,
+  videoRef: RefObject<HTMLVideoElement | null>,
+  onIdle?: () => void,
+) {
+  const [showOverlays, setShowOverlays] = useState(true);
+  const [needsInteraction, setNeedsInteraction] = useState(false);
+  const idleTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+  // Keep onIdle in a ref so resetIdle doesn't need it as a dep
+  const onIdleRef = useRef(onIdle);
+  useEffect(() => {
+    onIdleRef.current = onIdle;
+  });
+
+  const resetIdle = useCallback(() => {
+    setShowOverlays(true);
+    setNeedsInteraction(false);
+    if (idleTimer.current) clearTimeout(idleTimer.current);
+    idleTimer.current = setTimeout(() => {
+      setShowOverlays(false);
+      onIdleRef.current?.();
+    }, timeoutMs);
+    videoRef.current?.play().catch(() => {});
+  }, [timeoutMs, videoRef]);
+
+  useEffect(() => {
+    resetIdle();
+    return () => {
+      if (idleTimer.current) clearTimeout(idleTimer.current);
+    };
+  }, [resetIdle]);
+
+  return { showOverlays, needsInteraction, setNeedsInteraction, resetIdle };
+}