feat: add setting to disable tag-color row tint in message list

Message-list rows are tinted with the first tag's color, which becomes
overwhelming when a label applies to most messages (for example
per-account labels). Add a `tintListRowsByTag` setting (default true, so
current behavior is unchanged) with a toggle in Settings beside
"Colorful Sidebar Icons". When off, rows are not tinted; tag dots and
chips still show the color. Gated in both list renderers
(email-list-item and thread-list-item).

locales/pt/common.json

@@ -938,6 +938,10 @@
         "label": "Ícones coloridos na barra lateral",
         "description": "Colorir ícones de pastas e etiquetas por tipo (Caixa de entrada azul, Spam vermelho, Enviados verde, etc.). Desative para uma barra lateral monocromática."
       },
+      "tint_list_rows": {
+        "label": "Tint List Rows by Tag Color",
+        "description": "Shade each message row with its first tag color. Disable to keep rows plain; tag dots and chips still show the color."
+      },
       "show_folder_total_count": {
         "label": "Mostrar contagem total de mensagens",
         "description": "Mostra a contagem total de mensagens ao lado de pastas e etiquetas, além da contagem de não lidas. Desative para mostrar apenas as não lidas."