Fix 500 in cancellazione partita con recording collegato.

Distruggendo la sessione ora si elimina anche il recording, evitando la violazione FK su recordings.

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

backend/app/models/stream_session.rb

@@ -15,7 +15,7 @@ class StreamSession < ApplicationRecord
   has_many :attempted_concurrency_violations, class_name: "StreamConcurrencyViolation",
            foreign_key: :attempted_session_id, dependent: :nullify, inverse_of: :attempted_session
   has_one :score_state, dependent: :destroy
-  has_one :recording
+  has_one :recording, dependent: :destroy
   has_many :device_states, dependent: :destroy
 
   validates :platform, inclusion: { in: PLATFORMS }