Aggiunge registry nodi stream e provisioning Hetzner/lab per lo scale-out.

Prepara l'architettura multi-nodo (MediaMTX+ffmpeg) con assignment URL per sessione, admin di provision/drain e provider Cloud/DNS astratti verso mltv-stream.net.

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

backend/db/seeds.rb

@@ -43,3 +43,6 @@ end
 
 puts "Seed OK: coach@matchlivetv.test / Password123"
 puts "Club: #{club.name}, Team: #{team.name}, Match: #{match.opponent_name}"
+
+home = Streams::NodeRegistry.ensure_home_from_env!
+puts "Stream node home: #{home.slug} rtmp=#{home.rtmp_base_url}"