feat: redesign match play and add broadcast tooling

scripts/migrations/0008-broadcast.sql

@@ -0,0 +1,13 @@
+-- Stream channels: what an overlay shows and how it is laid out.
+CREATE TABLE IF NOT EXISTS broadcast_channel (
+	id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+	name text NOT NULL,
+	mode text NOT NULL DEFAULT 'auto',
+	match_id uuid REFERENCES match(id) ON DELETE SET NULL,
+	tournament_id uuid REFERENCES tournament(id) ON DELETE CASCADE,
+	layout jsonb NOT NULL,
+	agent_token_hash text,
+	created_by text,
+	created_at timestamptz NOT NULL DEFAULT now(),
+	updated_at timestamptz NOT NULL DEFAULT now()
+);