Make video a per-server toggle instead of an env-wide setting

VIDEO_ENABLED is now permission rather than behaviour: it decides whether
the feature exists at all, while turning it on for a server is a toggle in
the panel or !video in chat, off by default. Video costs real CPU for
every playing channel, so that should be a deliberate choice rather than
something a config flag switches on everywhere.

With the env flag off the panel renders no toggle at all and !video says
so, and the switch applies from the next track — swapping tracks mid-play
would cut the current one.

The loop button no longer reads "выкл" either: it sat next to the video
button showing the same word, so the two states were indistinguishable.
Both now name what they do and rely on highlighting for state.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/App.tsx

@@ -183,6 +183,7 @@ export function App() {
               voiceChannels={voiceChannels}
               yourVoiceChannel={yourVoiceChannel}
               requireListener={me.features.requireListener}
+              videoAvailable={me.features.video}
               onAction={(action, payload) => void runAction(action, payload)}
               onSeek={(seconds) => void runAction("seek", { position: seconds })}
               onJoin={(channelId) => {

web/src/components/NowPlaying.tsx

@@ -9,6 +9,8 @@ interface Props {
   voiceChannels: VoiceChannel[];
   yourVoiceChannel: VoiceChannel | null;
   requireListener: boolean;
+  /** Hidden entirely when the bot was built without video support. */
+  videoAvailable: boolean;
   onAction(action: string, payload?: Record<string, unknown>): void;
   onSeek(seconds: number): void;
   onJoin(channelId: string | null): void;
@@ -23,7 +25,7 @@ const STATUS_LABEL: Record<PlayerState["status"], string> = {
 };
 
 const LOOP_LABEL: Record<LoopMode, string> = {
-  off: "🔁 выкл",
+  off: "🔁 повтор",
   track: "🔂 трек",
   queue: "🔁 очередь",
 };
@@ -35,6 +37,7 @@ export function NowPlaying({
   voiceChannels,
   yourVoiceChannel,
   requireListener,
+  videoAvailable,
   onAction,
   onSeek,
   onJoin,
@@ -141,6 +144,21 @@ export function NowPlaying({
           {LOOP_LABEL[state.loop]}
         </button>
 
+        {videoAvailable && (
+          <button
+            className={state.videoEnabled ? "active" : ""}
+            onClick={() => onAction("video", { enabled: !state.videoEnabled })}
+            disabled={!canControl}
+            title={
+              state.videoEnabled
+                ? "Клип показывается как демонстрация экрана — нажмите, чтобы выключить"
+                : "Показывать клип как демонстрацию экрана (со следующего трека)"
+            }
+          >
+            📺 видео
+          </button>
+        )}
+
         <div className="volume">
           <span title="Громкость">🔊</span>
           <input

web/src/types.ts

@@ -26,6 +26,7 @@ export interface PlayerState {
   history: Track[];
   volume: number;
   loop: LoopMode;
+  videoEnabled: boolean;
   updatedAt: number;
 }
 
@@ -43,7 +44,7 @@ export interface ServerRef {
 export interface Me {
   user: { id: string; username: string };
   servers: ServerRef[];
-  features: { localLibrary: boolean; requireListener: boolean };
+  features: { localLibrary: boolean; requireListener: boolean; video: boolean };
 }
 
 export interface ServerStateResponse {