i18n: localize the editor toolbar in all 23 locales

The rich-text editor was the last hardcoded-English surface in the
composer: 21 tooltip titles, the eight table-menu entries, the "Remove
color" entry and the table size picker's "Pick size" label were plain
strings while every other menu in the app is localized.

All of them now come from a new email_composer.toolbar namespace,
translated into all 23 locales using each platform's established
editor terminology (Word/Docs conventions - de "Formatierung löschen",
ar "مسح التنسيق", ja "書式をクリア", ...). The link prompt stays "URL",
which is the same term in every language.

Tooltips and self-sizing dropdowns have no width constraints, so longer
translations are safe everywhere.

locales/fr/common.json

@@ -686,6 +686,38 @@
     "recipient_name_placeholder": "Nom d'affichage",
     "autocomplete_search_server": "Rechercher sur le serveur",
     "autocomplete_searching": "Recherche en cours...",
+    "toolbar": {
+      "bold": "Gras",
+      "italic": "Italique",
+      "underline": "Souligné",
+      "strikethrough": "Barré",
+      "text_color": "Couleur du texte",
+      "remove_color": "Supprimer la couleur",
+      "heading_1": "Titre 1",
+      "heading_2": "Titre 2",
+      "bullet_list": "Liste à puces",
+      "ordered_list": "Liste numérotée",
+      "quote": "Citation",
+      "code_block": "Bloc de code",
+      "align_left": "Aligner à gauche",
+      "align_center": "Centrer",
+      "align_right": "Aligner à droite",
+      "text_direction": "Sens du texte (RTL/LTR)",
+      "link": "Lien",
+      "table": "Tableau",
+      "clear_formatting": "Effacer la mise en forme",
+      "undo": "Annuler",
+      "redo": "Rétablir",
+      "add_row_above": "Insérer une ligne au-dessus",
+      "add_row_below": "Insérer une ligne en dessous",
+      "add_column_before": "Insérer une colonne avant",
+      "add_column_after": "Insérer une colonne après",
+      "delete_row": "Supprimer la ligne",
+      "delete_column": "Supprimer la colonne",
+      "toggle_header_row": "Basculer la ligne d'en-tête",
+      "delete_table": "Supprimer le tableau",
+      "pick_size": "Choisir la taille"
+    },
     "send_filing_warning": "Envoyé - mais le nettoyage après envoi a échoué, un ancien brouillon peut subsister."
   },
   "confirm_dialog": {