Introduce architettura multi-sport con catalogo, engine scoring e overlay.

Catalogo sport in YAML, board implicito, engine per volley/basket/timed/racket/timer/generic, regia e app Android allineate.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/db/migrate/20260609100000_multi_sport.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class MultiSport < ActiveRecord::Migration[7.2]
+  def up
+    rename_column :teams, :sport, :sport_key
+    rename_column :matches, :sport, :sport_key
+
+    change_column_default :teams, :sport_key, from: "volleyball", to: "pallavolo"
+    change_column_default :matches, :sport_key, from: "volleyball", to: "pallavolo"
+
+    execute <<~SQL.squish
+      UPDATE teams SET sport_key = 'pallavolo' WHERE sport_key = 'volleyball' OR sport_key IS NULL OR sport_key = '';
+      UPDATE matches SET sport_key = 'pallavolo' WHERE sport_key = 'volleyball' OR sport_key IS NULL OR sport_key = '';
+    SQL
+
+    add_column :matches, :overlay_kind, :string
+    add_column :score_states, :board_type, :string, null: false, default: "volley"
+    add_column :score_states, :data, :jsonb, null: false, default: {}
+
+    execute <<~SQL.squish
+      UPDATE matches
+      SET scoring_rules = scoring_rules || jsonb_build_object('sets_to_win', sets_to_win)
+      WHERE sets_to_win IS NOT NULL
+        AND NOT (scoring_rules ? 'sets_to_win');
+    SQL
+
+    execute <<~SQL.squish
+      UPDATE score_states ss
+      SET board_type = 'volley'
+      FROM stream_sessions s
+      JOIN matches m ON m.id = s.match_id
+      WHERE ss.stream_session_id = s.id;
+    SQL
+  end
+
+  def down
+    execute <<~SQL.squish
+      UPDATE teams SET sport_key = 'volleyball' WHERE sport_key = 'pallavolo';
+      UPDATE matches SET sport_key = 'volleyball' WHERE sport_key = 'pallavolo';
+    SQL
+
+    change_column_default :teams, :sport_key, from: "pallavolo", to: "volleyball"
+    change_column_default :matches, :sport_key, from: "pallavolo", to: "volleyball"
+
+    rename_column :teams, :sport_key, :sport
+    rename_column :matches, :sport_key, :sport
+
+    remove_column :matches, :overlay_kind
+    remove_column :score_states, :board_type
+    remove_column :score_states, :data
+  end
+end