feat: implement email keyword management with color tagging

- Introduced a new settings section for managing email keywords (labels/tags) with associated colors.
- Updated email context menu, viewer, and list item components to support the new keyword system.
- Refactored color tag handling to accommodate both new $label: and legacy $color: prefixes.
- Added utility functions for retrieving email color tags based on keywords.
- Enhanced localization files to include translations for the new keyword management features.
- Updated the settings store to manage keyword definitions, including add, update, delete, and reorder functionalities.
- Added tests for the new keyword handling logic.

locales/fr/common.json

@@ -447,7 +447,8 @@
       "calendar": "Calendrier",
       "filters": "Filtres",
       "templates": "Modèles",
-      "folders": "Dossiers"
+      "folders": "Dossiers",
+      "keywords": "Mots-clés"
     },
     "tab_groups": {
       "general": "Général",
@@ -487,6 +488,23 @@
         "description": "Afficher les transitions et effets fluides"
       }
     },
+    "keywords": {
+      "title": "Mots-clés des e-mails",
+      "description": "Définissez des mots-clés (étiquettes) pour organiser vos e-mails avec des couleurs.",
+      "add_keyword": "Ajouter un mot-clé",
+      "reset_defaults": "Réinitialiser par défaut",
+      "label_field": "Nom d'affichage",
+      "label_placeholder": "ex. Travail, Personnel, Urgent",
+      "id_field": "ID du mot-clé",
+      "id_placeholder": "ex. travail, personnel",
+      "color_field": "Couleur",
+      "id_exists": "Cet ID de mot-clé existe déjà",
+      "edit": "Modifier le mot-clé",
+      "delete": "Supprimer le mot-clé",
+      "save": "Enregistrer",
+      "add": "Ajouter",
+      "cancel": "Annuler"
+    },
     "language_region": {
       "title": "Langue et région",
       "description": "Configurez vos préférences linguistiques et régionales",