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/streams/overlay.rb

@@ -0,0 +1,35 @@
+module Streams
+  module Overlay
+    module_function
+
+    def overlay_dir(session_id)
+      Rails.root.join("tmp/stream_overlays", session_id.to_s)
+    end
+
+    def overlay_png_path(session)
+      overlay_dir(session.id).join("overlay.png")
+    end
+
+    def overlay_pipe_path(session)
+      overlay_dir(session.id).join("overlay.pipe")
+    end
+
+    def badge_away_color(team)
+      club = team.club
+      candidate = club&.effective_secondary_color.presence || "#1565c0"
+      return candidate unless light_hex_color?(candidate)
+
+      "#1565c0"
+    end
+
+    def light_hex_color?(hex)
+      h = hex.to_s.delete_prefix("#")
+      return false unless h.match?(/\A\h{6}\z/i)
+
+      r = h[0..1].to_i(16)
+      g = h[2..3].to_i(16)
+      b = h[4..5].to_i(16)
+      (0.299 * r + 0.587 * g + 0.114 * b) > 200
+    end
+  end
+end