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>

src/bot/commands.ts

@@ -260,6 +260,26 @@ export const commands: Command[] = [
       await ctx.reply(`🔁 Повтор: ${loopLabel(nextMode)}`);
     },
   },
+  {
+    name: "video",
+    aliases: ["видео"],
+    usage: "video [on|off]",
+    description: "Показывать клип как демонстрацию экрана",
+    async run(ctx) {
+      if (!config.VIDEO_ENABLED) {
+        throw new UserFacingError("Видео выключено в настройках бота (VIDEO_ENABLED)");
+      }
+      const raw = (ctx.args[0] ?? "").toLowerCase();
+      const current = ctx.manager.snapshot(ctx.serverId).videoEnabled;
+      const next = raw ? ["on", "вкл", "true", "1", "да"].includes(raw) : !current;
+      await ctx.manager.setVideo(ctx.serverId, ctx.actor.id, next);
+      await ctx.reply(
+        next
+          ? "📺 Клип будет показан как демонстрация экрана — со следующего трека."
+          : "🔇 Видео выключено, играю только звук.",
+      );
+    },
+  },
   {
     name: "shuffle",
     aliases: ["sh", "перемешай"],
@@ -348,7 +368,9 @@ export const commands: Command[] = [
     usage: "help",
     description: "Показать список команд",
     async run(ctx) {
-      const lines = commands.map(
+      const lines = commands
+        .filter((command) => command.name !== "video" || config.VIDEO_ENABLED)
+        .map(
         (command) => `\`${config.COMMAND_PREFIX}${command.usage}\` — ${command.description}`,
       );
       await ctx.reply(