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/app/services/streams/dns_providers/hetzner.rb

@@ -0,0 +1,105 @@
+# frozen_string_literal: true
+
+require "faraday"
+require "cgi"
+
+module Streams
+  module DnsProviders
+    # Hetzner Cloud DNS (Console) — zone mltv-stream.net.
+    #
+    # ENV:
+    #   HCLOUD_TOKEN (stesso del Cloud)
+    #   STREAM_DNS_ZONE (default mltv-stream.net)
+    #   STREAM_DNS_TTL (default 60)
+    class Hetzner < Base
+      API = "https://api.hetzner.cloud/v1"
+
+      def initialize(token: ENV.fetch("HCLOUD_TOKEN"), zone: nil, conn: nil)
+        @token = token
+        @zone = zone || ENV.fetch("STREAM_DNS_ZONE", "mltv-stream.net")
+        @ttl = ENV.fetch("STREAM_DNS_TTL", "60").to_i
+        @conn = conn
+      end
+
+      def upsert_a(name, ip)
+        rr_name = relative_name(name)
+        delete_a(name)
+        post("/zones/#{CGI.escape(@zone)}/rrsets", {
+          name: rr_name,
+          type: "A",
+          ttl: @ttl,
+          records: [{ value: ip.to_s, comment: "matchlivetv stream-node" }],
+          labels: { "matchlivetv" => "true", "role" => "stream-node" }
+        })
+        true
+      end
+
+      def delete_a(name)
+        rr_name = relative_name(name)
+        encoded = CGI.escape(rr_name)
+        response = conn.delete("/zones/#{CGI.escape(@zone)}/rrsets/#{encoded}/A") do |req|
+          req.headers.update(auth_headers)
+        end
+        return true if response.status == 404 || response.status == 204 || response.success?
+
+        raise Error, "Hetzner DNS API #{response.status}: #{response.body.inspect}"
+      end
+
+      def resolve(name)
+        rr_name = relative_name(name)
+        data = get("/zones/#{CGI.escape(@zone)}/rrsets", name: rr_name, type: "A")
+        rrset = Array(data["rrsets"]).first
+        Array(rrset&.dig("records")).first&.dig("value")
+      rescue Error
+        nil
+      end
+
+      private
+
+      def relative_name(name)
+        host = name.to_s.strip.downcase.delete_suffix(".")
+        suffix = ".#{@zone}"
+        return "@" if host == @zone
+        return host.delete_suffix(suffix) if host.end_with?(suffix)
+
+        host
+      end
+
+      def conn
+        @conn ||= Faraday.new(url: API) do |f|
+          f.request :json
+          f.response :json, content_type: /\bjson$/
+          f.adapter Faraday.default_adapter
+        end
+      end
+
+      def auth_headers
+        { "Authorization" => "Bearer #{@token}" }
+      end
+
+      def get(path, params = {})
+        response = conn.get(path) do |req|
+          req.headers.update(auth_headers)
+          req.params.update(params)
+        end
+        unwrap!(response)
+      end
+
+      def post(path, body)
+        response = conn.post(path) do |req|
+          req.headers.update(auth_headers)
+          req.body = body
+        end
+        unwrap!(response)
+      end
+
+      def unwrap!(response)
+        unless response.success?
+          raise Error, "Hetzner DNS API #{response.status}: #{response.body.inspect}"
+        end
+
+        response.body.is_a?(Hash) ? response.body : {}
+      end
+    end
+  end
+end