feat(music): add /music toggle and gate playback behind it

Music could be started and controlled with no way to turn it off for
a server. Adds a music_settings table (mirrors the same one
velox-dashboard-api's dashboard toggle reads/writes), a /music toggle
command gated to Manage Server, and checks in /play, /queue, and
/volume so they refuse to run when a server has music turned off.

schema.sql

@@ -133,3 +133,42 @@ CREATE TABLE IF NOT EXISTS user_settings (
     user_id BIGINT PRIMARY KEY,
     timezone TEXT NOT NULL
 );
+
+--
+-- Music (dashboard queue view/control - see velox-dashboard-api's
+-- 000010_music migration, this file mirrors it)
+--
+CREATE TABLE IF NOT EXISTS music_settings (
+    guild_id BIGINT PRIMARY KEY,
+    is_enabled BOOLEAN NOT NULL DEFAULT FALSE
+);
+
+CREATE TABLE IF NOT EXISTS music_now_playing (
+    guild_id BIGINT PRIMARY KEY,
+    track_title TEXT NOT NULL,
+    track_url TEXT NOT NULL,
+    duration_seconds INT NOT NULL,
+    started_at TIMESTAMPTZ NOT NULL,
+    paused BOOLEAN NOT NULL DEFAULT FALSE,
+    volume INT NOT NULL DEFAULT 100
+);
+
+CREATE TABLE IF NOT EXISTS music_queue (
+    id BIGSERIAL PRIMARY KEY,
+    guild_id BIGINT NOT NULL,
+    position INT NOT NULL,
+    track_title TEXT NOT NULL,
+    track_url TEXT NOT NULL,
+    requested_by BIGINT NOT NULL,
+    added_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS music_commands (
+    id BIGSERIAL PRIMARY KEY,
+    guild_id BIGINT NOT NULL,
+    command_type TEXT NOT NULL CHECK (command_type IN ('skip', 'pause', 'resume', 'set_volume', 'remove_track', 'reorder')),
+    payload JSONB,
+    requested_by BIGINT NOT NULL,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    processed_at TIMESTAMPTZ
+);