Rendi affidabile pausa con slate e conferma i controlli laterali.

Evita buchi HLS/YouTube in pausa (path slate ricreata, reload player, no patch recording inutili) e richiede conferma su tasti laterali app/regia.

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

backend/app/services/streams/cover_slate_paths.rb

@@ -4,10 +4,15 @@ module Streams
       ENV.fetch("MEDIAMTX_SLATES_CUSTOM_DIR", "/slates/custom")
     end
 
+    # ActiveStorage checksum is base64 e può contenere "/", "+", "=" — non usabile come path.
+    def self.safe_digest(checksum)
+      checksum.to_s.tr("+/", "-_").delete("=")
+    end
+
     def self.filename_for(record)
       return nil unless record.cover_slate.attached?
 
-      digest = record.cover_slate.blob.checksum
+      digest = safe_digest(record.cover_slate.blob.checksum)
       prefix = record.class.name.underscore
       "#{prefix}-#{record.id}-#{digest}.mp4"
     end