feat: smart note history with manual/auto modes, delete entries, i18n fixes

- Add noteHistoryMode setting (manual default / auto) with DB migration
- Manual mode: commit button in editor toolbar creates snapshots on demand
- Auto mode: smart snapshots with 20-char diff threshold + 5min cooldown,
  structural changes (color, pin, archive, labels) bypass cooldown
- Add delete individual history entries from history modal
- Fix sidebar: Notes nav no longer active on notebook pages
- Fix sidebar icon: replace filled Lightbulb with outlined FileText
- Fix title suggestions: change from amber to sky blue color scheme
- Fix hydration mismatch: add suppressHydrationWarning on locale dates
- Complete i18n: add history, sort, and AI chat translations for all 16 languages
- Translate French AI assistant section (40+ keys) from English to French
- Update README with new features and stack info

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/locales/en.json

@@ -161,7 +161,29 @@
     "notes.emptyNotebook": "Empty notebook",
     "notes.emptyNotebookDesc": "This notebook has no notes. Click + to create one.",
     "notes.noNoteSelected": "No note selected",
-    "notes.selectOrCreateNote": "Select a note from the list or create a new one."
+    "notes.selectOrCreateNote": "Select a note from the list or create a new one.",
+    "commitVersion": "Save version",
+    "versionSaved": "Version saved",
+    "deleteVersion": "Delete this version",
+    "versionDeleted": "Version deleted",
+    "deleteVersionConfirm": "Delete this version permanently?",
+    "historyMode": "History mode",
+    "historyModeManual": "Manual (commit button)",
+    "historyModeAuto": "Automatic (smart)",
+    "historyModeManualDesc": "Create snapshots manually with the commit button",
+    "historyModeAutoDesc": "Automatic snapshots with smart detection",
+    "history": "History",
+    "historyRestored": "Version restored",
+    "historyEnabled": "History enabled",
+    "historyDisabledDesc": "History is disabled for your account.",
+    "enableHistory": "Enable history",
+    "historyEmpty": "No versions available",
+    "historySelectVersion": "Select a version to preview its content",
+    "sortBy": "Sort by",
+    "sortDateDesc": "Date (newest)",
+    "sortDateAsc": "Date (oldest)",
+    "sortTitleAsc": "Title A → Z",
+    "sortTitleDesc": "Title Z → A"
   },
   "pagination": {
     "previous": "←",