fix: i18n for dashboard widgets + shortcuts — no more hardcoded French

Replaced all hardcoded French text in dashboard.js with t() calls:
- 'Chargement...' → t('common.loading')
- 'Erreur:' → t('dashboard.error_prefix')
- Size units ('o','Ko','Mo','Go') → t('dashboard.size_*')
- 'fichier(s)' → t('dashboard.count_files*')
- '0 fichiers' → t('dashboard.zero_files')
- 'Conflits de synchronisation' → t('dashboard.conflicts_title')
- 'Garder l\'original'/'Garder le conflit' → t('dashboard.keep_*')
- 'Ajouter/Retirer des bookmarks' → t('dashboard.bookmark_*')
- 'à l\'instant'/'il y a X min/h/j' → t('dashboard.*_ago', {n})
- 'Afficher'/'Masquer' → t('dashboard.show/hide')
- 'Erreur de chargement' → t('dashboard.load_error')

Added 11 shortcut i18n keys + 22 dashboard i18n keys to en.json/fr.json.

Verified: '4 files' count, English shortcuts, English empty states.

frontend/locales/fr.json

@@ -447,12 +447,29 @@
   "conflict.resolve_conflict": "Garder version conflit",
   "conflict.resolve_local": "Garder version locale",
   "conflict.resolved": "Conflit résolu",
+  "dashboard.all_vaults": "Tous les vaults",
+  "dashboard.bookmark_add": "Ajouter aux bookmarks",
+  "dashboard.bookmark_remove": "Retirer des bookmarks",
   "dashboard.bookmarks": "Favoris",
+  "dashboard.conflict_date": "Conflit du ",
   "dashboard.conflict_resolved": "Conflit résolu",
   "dashboard.conflicts": "Conflits",
+  "dashboard.conflicts_title": "Conflits de synchronisation",
   "dashboard.copy_btn": "Copier",
+  "dashboard.count_files": "fichier",
+  "dashboard.count_files_plural": "fichiers",
   "dashboard.ctrl_hover_tip": "Survolez un document avec Ctrl pour un aperçu rapide. Cliquez sur Forge dans la barre d'outils pour l'éditeur avancé.",
+  "dashboard.day_ago": "il y a {n} j",
+  "dashboard.error_prefix": "Erreur: ",
   "dashboard.expires": "Expire le {date}",
+  "dashboard.hide": "Masquer",
+  "dashboard.hour_ago": "il y a {n} h",
+  "dashboard.just_now": "à l'instant",
+  "dashboard.keep_conflict": "Garder le conflit",
+  "dashboard.keep_original": "Garder l'original",
+  "dashboard.load_error": "Erreur de chargement",
+  "dashboard.loading": "Chargement...",
+  "dashboard.min_ago": "il y a {n} min",
   "dashboard.no_bookmarks": "Aucun favori",
   "dashboard.no_conflicts": "Aucun conflit",
   "dashboard.no_recent": "Aucun fichier récent",
@@ -465,6 +482,11 @@
   "dashboard.recent_hint": "Ouvrez un fichier pour le voir apparaître ici",
   "dashboard.shared_hint": "Partagez un document pour le voir apparaître ici",
   "dashboard.shares": "Partages",
+  "dashboard.show": "Afficher",
+  "dashboard.size_bytes": " o",
+  "dashboard.size_gb": " Go",
+  "dashboard.size_kb": " Ko",
+  "dashboard.size_mb": " Mo",
   "dashboard.stats": "Statistiques",
   "dashboard.stats_files": "Fichiers",
   "dashboard.stats_size": "Taille totale",
@@ -479,6 +501,7 @@
   "dashboard.vaults_count": "Vaults",
   "dashboard.views": "{count} vue(s)",
   "dashboard.welcome": "Bienvenue dans ObsiGate",
+  "dashboard.zero_files": "0 fichiers",
   "dragdrop.cross_vault_unsupported": "Cross-vault moves are not supported",
   "dragdrop.move_failed": "Move failed",
   "editor.cancel": "Annuler",
@@ -1213,6 +1236,17 @@
   "share.never": "Jamais",
   "share.revoke": "Révoquer",
   "share.title": "Partage public",
+  "shortcut.ai_completion": "Completion IA inline (dans l'éditeur)",
+  "shortcut.close_editor": "Fermer l'éditeur / modale",
+  "shortcut.command_palette": "Palette de commandes",
+  "shortcut.editor_help": "Aide de l'éditeur Forge",
+  "shortcut.file_palette": "Palette de fichiers (nav. rapide)",
+  "shortcut.focus_search": "Focus barre de recherche",
+  "shortcut.quick_insert": "Insertion rapide (éditeur Forge)",
+  "shortcut.quick_search": "Recherche rapide (hors champ texte)",
+  "shortcut.save_file": "Sauvegarder le fichier ouvert",
+  "shortcut.search_in_doc": "Rechercher dans le document",
+  "shortcut.tip_preview": "Survolez un document avec **Ctrl** pour un aperçu rapide. Cliquez sur **Forge** dans la barre d'outils pour l'éditeur avancé.",
   "sidebar.all_vaults": "Tous les vaults",
   "sidebar.case_sensitive": "Respecter la casse",
   "sidebar.clear_filter": "Effacer",