i18n: fix dashboard tabs and shortcut descriptions

- Dashboard tabs: Statistiques/Récents/Partagés -> data-i18n spans
- Shortcut descriptions: added 10 help.shortcut_* keys to locales
- Tip text: added help.shortcut_tip key
- Added 3 dashboard.tab_* keys
- en.json/fr.json: 1044 -> 1059 keys

frontend/locales/en.json

@@ -1040,5 +1040,19 @@
   "dashboard.stats_size": "Total size",
   "dashboard.stats_tags": "Unique tags",
   "dashboard.stats_vaults": "Vaults",
-  "help.shortcuts_title": "Shortcuts & Tips"
+  "help.shortcuts_title": "Shortcuts & Tips",
+  "help.shortcut_command_palette": "Command palette",
+  "help.shortcut_quick_search": "Quick search (outside text field)",
+  "help.shortcut_close_editor": "Close editor / modal",
+  "help.shortcut_forge_help": "Forge editor help",
+  "help.shortcut_file_palette": "File palette (quick nav.)",
+  "help.shortcut_save_file": "Save open file",
+  "help.shortcut_ai_completion": "Inline AI completion (in editor)",
+  "help.shortcut_focus_search": "Focus search bar",
+  "help.shortcut_search_doc": "Search in document",
+  "help.shortcut_quick_insert": "Quick insert (Forge editor)",
+  "help.shortcut_tip": "Hover over a document with <strong>Ctrl</strong> for a quick preview. Click <strong>Forge</strong> in the toolbar for the advanced editor.",
+  "dashboard.tab_stats": "Statistics",
+  "dashboard.tab_recent": "Recent",
+  "dashboard.tab_shared": "Shared"
 }