Aggiunge overlay server-side burn-in e stabilizza diretta live.

Tabellone, badge e brand sono ricodificati nel flusso _air via OverlayRelay;
sync punteggio HTTP, volume condiviso rails/sidekiq, qualità 720p migliorata
e badge CONNECTING in ripresa da pausa.

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

backend/app/services/scoring/apply_action.rb

@@ -105,6 +105,7 @@ module Scoring
 
     def broadcast(score)
       SessionChannel.broadcast_message(@session, score.as_cable_payload)
+      Streams::Overlay::Refresh.call(@session)
     end
   end
 end

backend/app/services/scoring/sync_state.rb

@@ -0,0 +1,28 @@
+module Scoring
+  # Sincronizza lo stato completo del tabellone (app mobile / Action Cable).
+  class SyncState
+    SCORE_KEYS = %w[home_sets away_sets home_points away_points current_set].freeze
+
+    def initialize(session:, payload:)
+      @session = session
+      @payload = payload.stringify_keys
+    end
+
+    def call
+      score = @session.score_state || @session.create_score_state!(
+        home_sets: 0, away_sets: 0, home_points: 0, away_points: 0, current_set: 1, set_partials: []
+      )
+
+      attrs = {}
+      SCORE_KEYS.each do |key|
+        attrs[key] = @payload[key] if @payload.key?(key)
+      end
+      attrs[:set_partials] = @payload["set_partials"] if @payload.key?("set_partials")
+
+      score.update!(attrs)
+      SessionChannel.broadcast_message(@session, score.as_cable_payload)
+      Streams::Overlay::Refresh.call(@session)
+      score
+    end
+  end
+end