[mirotalksfu] - add env BRAND_HTML_INJECTION

.env.template

@@ -220,6 +220,9 @@ AWS_REGION=                                       # AWS region (e.g., us-east-2,
 # 8. UI Customization
 # ----------------------------------------------------
 
+# Branding injection
+BRAND_HTML_INJECTION=true                         # Enable HTML injection for branding (true|false)
+
 # App
 UI_LANGUAGE=en                                    # Interface language (en, es, fr, etc.)
 APP_NAME=MiroTalk SFU                             # Application name