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- Fix sidebar: Notes nav no longer active on notebook pages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/app/actions/ai-settings.ts

@@ -21,6 +21,8 @@ export type UserAISettingsData = {
   fontSize?: 'small' | 'medium' | 'large'
   languageDetection?: boolean
   autoLabeling?: boolean
+  noteHistory?: boolean
+  noteHistoryMode?: 'manual' | 'auto'
 }
 
 /** Only fields that exist on `UserAISettings` in Prisma (excludes e.g. `theme`, which lives on `User`). */
@@ -41,6 +43,8 @@ const USER_AI_SETTINGS_PRISMA_KEYS = [
   'anonymousAnalytics',
   'languageDetection',
   'autoLabeling',
+  'noteHistory',
+  'noteHistoryMode',
 ] as const
 
 type UserAISettingsPrismaKey = (typeof USER_AI_SETTINGS_PRISMA_KEYS)[number]
@@ -151,6 +155,8 @@ const getCachedAISettings = unstable_cache(
           fontSize: 'medium' as const,
           languageDetection: true,
           autoLabeling: true,
+          noteHistory: false,
+          noteHistoryMode: 'manual' as const,
         }
       }
 
@@ -180,6 +186,8 @@ const getCachedAISettings = unstable_cache(
         fontSize: (settings.fontSize || 'medium') as 'small' | 'medium' | 'large',
         languageDetection: settings.languageDetection ?? true,
         autoLabeling: settings.autoLabeling ?? true,
+        noteHistory: settings.noteHistory ?? false,
+        noteHistoryMode: (settings.noteHistoryMode ?? 'manual') as 'manual' | 'auto',
       }
     } catch (error) {
       console.error('Error getting AI settings:', error)
@@ -202,6 +210,8 @@ const getCachedAISettings = unstable_cache(
         fontSize: 'medium' as const,
         languageDetection: true,
         autoLabeling: true,
+        noteHistory: false,
+        noteHistoryMode: 'manual' as const,
       }
     }
   },
@@ -237,6 +247,8 @@ export async function getAISettings(userId?: string) {
       fontSize: 'medium' as const,
       languageDetection: true,
       autoLabeling: true,
+      noteHistory: false,
+      noteHistoryMode: 'manual' as const,
     }
   }
 
@@ -266,6 +278,8 @@ export async function isAIFeatureEnabled(feature: keyof UserAISettingsData): Pro
       return settings.paragraphRefactor
     case 'memoryEcho':
       return settings.memoryEcho
+    case 'noteHistory':
+      return settings.noteHistory
     default:
       return true
   }