Stabilizza live YouTube/RTMP e fix crash rotazione mobile.

Pipeline YouTube con relay, overlay e publisher sync lato backend; fix GL pauseGlDuringRotation su Android per evitare crash in rotazione durante lo streaming Flutter.

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

backend/app/services/streams/overlay/svg_builder.rb

@@ -1,6 +1,6 @@
 module Streams
   module Overlay
-    # PNG 1280×720 trasparente: tabellone alto-sinistra, badge alto-destra, brand sotto tabellone.
+    # PNG 1280×720 trasparente: tabellone alto-sinistra, badge alto-destra, logo chiaro (logo-white-m) basso-destra.
     class SvgBuilder
       CANVAS_W = 1280
       CANVAS_H = 720
@@ -17,9 +17,10 @@ module Streams
         cols = score_columns
         <<~SVG
           <?xml version="1.0" encoding="UTF-8"?>
-          <svg xmlns="http://www.w3.org/2000/svg" width="#{CANVAS_W}" height="#{CANVAS_H}" viewBox="0 0 #{CANVAS_W} #{CANVAS_H}">
+          <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="#{CANVAS_W}" height="#{CANVAS_H}" viewBox="0 0 #{CANVAS_W} #{CANVAS_H}">
             #{scorebug_svg(cols)}
             #{badge_svg}
+            #{brand_watermark_svg}
           </svg>
         SVG
       end
@@ -113,6 +114,22 @@ module Streams
         SVG
       end
 
+      def brand_watermark_svg
+        path = Overlay.brand_logo_path
+        return "" unless path.file?
+
+        w = 108
+        h = 108
+        x = CANVAS_W - 14 - w
+        y = CANVAS_H - 14 - h
+        uri = "file://#{path.expand_path}"
+        <<~SVG
+          <g id="brand-watermark" opacity="0.94">
+            <image xlink:href="#{escape(uri)}" x="#{x}" y="#{y}" width="#{w}" height="#{h}" preserveAspectRatio="xMidYMid meet"/>
+          </g>
+        SVG
+      end
+
       def badge_svg
         text = @badge.text
         bg = @badge.background