Corregge il provisioning Hetzner: Faraday, cloud-init e default cpx12.

Sistemati path API /v1, AppArmor/auth MediaMTX sul nodo e defaults nbg1 così lo smoke Cloud è ripetibile.

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

backend/spec/services/streams/node_provisioner_spec.rb

@@ -15,6 +15,8 @@ RSpec.describe Streams::NodeProvisioner do
 
   before do
     redis.del(Streams::DnsProviders::Lab::REDIS_KEY)
+    StreamSession.where.not(stream_node_id: nil).update_all(stream_node_id: nil, status: "ended", ended_at: Time.current)
+    StreamNode.where.not(slug: Streams::NodeRegistry::HOME_SLUG).delete_all
   end
 
   it "provisions and decommissions a simulated lab node" do