feat: générateur d'exercices + planning de révision IA

- Générateur d'exercices : bouton dans menu note → IA crée 5 exercices
  - Niveaux variés (facile/moyen/difficile) avec emojis 🟢🟡🔴
  - Corrigés détaillés dans des toggles (cliquer pour révéler)
  - Callout warning pour le niveau
  - Notes créées dans le même carnet
- Planning de révision : bouton dans barre carnet → IA crée planning
  - Choix date d'examen
  - Répétition espacée (première lecture → revoir → révision globale)
  - Rappels automatiques ajoutés aux notes (9h le jour J)
  - Vue chronologique avec activités et notes par jour
- Services : exercise-generator.service.ts + study-planner.service.ts
- Endpoints : /api/ai/generate-exercises + /api/ai/study-plan
- i18n FR/EN complet

memento-note/app/api/ai/generate-exercises/route.ts

@@ -0,0 +1,98 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import prisma from '@/lib/prisma'
+import { exerciseGeneratorService } from '@/lib/ai/services/exercise-generator.service'
+import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'
+import { useLanguage } from '@/lib/i18n'
+
+export async function POST(request: NextRequest) {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const { noteId, count, language } = await request.json()
+    if (!noteId) {
+      return NextResponse.json({ error: 'noteId is required' }, { status: 400 })
+    }
+
+    try {
+      await checkEntitlementOrThrow(session.user.id, 'reformulate')
+    } catch (err) {
+      if (err instanceof QuotaExceededError) {
+        const isTierLocked = err.currentQuota === 0
+        return NextResponse.json(
+          { error: isTierLocked ? 'feature_locked' : 'quota_exceeded', errorKey: isTierLocked ? 'ai.featureLocked' : 'ai.quotaExceeded' },
+          { status: 402 },
+        )
+      }
+      throw err
+    }
+
+    const note = await prisma.note.findUnique({
+      where: { id: noteId },
+      select: { id: true, title: true, content: true, notebookId: true },
+    })
+
+    if (!note) {
+      return NextResponse.json({ error: 'Note not found' }, { status: 404 })
+    }
+
+    const exercises = await exerciseGeneratorService.generate(
+      note.title || 'Sans titre',
+      note.content,
+      { count: count || 5, language: language || 'fr' }
+    )
+
+    // Create exercise notes in the same notebook
+    const lang = language || 'fr'
+    const exerciseLabel = lang === 'fr' ? 'Exercice' : lang === 'fa' ? 'تمرین' : 'Exercise'
+    const answerLabel = lang === 'fr' ? 'Corrigé' : lang === 'fa' ? 'پاسخ' : 'Answer'
+
+    const createdNotes = []
+    for (let i = 0; i < exercises.length; i++) {
+      const ex = exercises[i]
+      const difficultyEmoji = ex.difficulty === 'facile' ? '🟢' : ex.difficulty === 'moyen' ? '🟡' : '🔴'
+
+      const content = `
+<div data-type="callout-block" data-callout-type="warning"><p><strong>${exerciseLabel} ${i + 1}</strong> — ${difficultyEmoji} ${ex.difficulty}</p></div>
+<h2>Énoncé</h2>
+<p>${ex.question}</p>
+<div data-type="toggle-block" data-opened="false"><p><strong>${answerLabel}</strong> — cliquer pour révéler</p><h3>Solution</h3><p>${ex.answer}</p></div>
+`.trim()
+
+      const created = await prisma.note.create({
+        data: {
+          title: `${exerciseLabel} ${i + 1} — ${note.title || ''}`,
+          content,
+          userId: session.user.id,
+          notebookId: note.notebookId,
+          type: 'richtext',
+          order: 999 + i,
+        },
+      })
+      createdNotes.push(created)
+
+      void (async () => {
+        try {
+          const { embeddingService } = await import('@/lib/ai/services/embedding.service')
+          const { upsertNoteEmbedding } = await import('@/lib/embeddings')
+          const { chunkIndexingService } = await import('@/lib/ai/services/chunk-indexing.service')
+          const { embedding } = await embeddingService.generateNoteEmbedding(created.title, content)
+          await upsertNoteEmbedding(created.id, embedding)
+          await chunkIndexingService.indexNote(created.id, created.title, content)
+        } catch {}
+      })()
+    }
+
+    incrementUsageAsync(session.user.id, 'reformulate')
+
+    return NextResponse.json({
+      exercises: createdNotes.map(n => ({ id: n.id, title: n.title })),
+    })
+  } catch (error: any) {
+    console.error('[Exercise Generator] Error:', error)
+    return NextResponse.json({ error: error.message || 'Failed to generate exercises' }, { status: 500 })
+  }
+}

memento-note/app/api/ai/study-plan/route.ts

@@ -0,0 +1,70 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import prisma from '@/lib/prisma'
+import { studyPlannerService } from '@/lib/ai/services/study-planner.service'
+import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'
+
+export async function POST(request: NextRequest) {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const { notebookId, examDate } = await request.json()
+    if (!notebookId || !examDate) {
+      return NextResponse.json({ error: 'notebookId and examDate are required' }, { status: 400 })
+    }
+
+    try {
+      await checkEntitlementOrThrow(session.user.id, 'reformulate')
+    } catch (err) {
+      if (err instanceof QuotaExceededError) {
+        const isTierLocked = err.currentQuota === 0
+        return NextResponse.json(
+          { error: isTierLocked ? 'feature_locked' : 'quota_exceeded', errorKey: isTierLocked ? 'ai.featureLocked' : 'ai.quotaExceeded' },
+          { status: 402 },
+        )
+      }
+      throw err
+    }
+
+    const notes = await prisma.note.findMany({
+      where: { notebookId, trashedAt: null, userId: session.user.id },
+      select: { id: true, title: true },
+      orderBy: { order: 'asc' },
+    })
+
+    if (notes.length === 0) {
+      return NextResponse.json({ error: 'No notes found in notebook' }, { status: 400 })
+    }
+
+    const userLang = await prisma.user.findUnique({
+      where: { id: session.user.id },
+      select: { theme: true },
+    })
+
+    const plan = await studyPlannerService.generate(notes, examDate)
+
+    // Set reminders on notes based on the plan
+    for (const day of plan.days) {
+      for (const noteId of day.noteIds) {
+        try {
+          const reminderDate = new Date(day.date)
+          reminderDate.setHours(9, 0, 0, 0)
+          await prisma.note.update({
+            where: { id: noteId },
+            data: { reminder: reminderDate },
+          })
+        } catch {}
+      }
+    }
+
+    incrementUsageAsync(session.user.id, 'reformulate')
+
+    return NextResponse.json(plan)
+  } catch (error: any) {
+    console.error('[Study Planner] Error:', error)
+    return NextResponse.json({ error: error.message || 'Failed to generate study plan' }, { status: 500 })
+  }
+}