feat(flashcards): révision SM-2, génération IA et page /revision

Livre US-FLASHCARDS avec decks, session de révision, stats et migration Prisma. Finalise le Web Clipper (i18n 15 langues) et corrige les erreurs ESLint bloquant la CI.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/app/api/flashcards/[id]/review/route.ts

@@ -0,0 +1,65 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import prisma from '@/lib/prisma'
+import { computeSm2Update } from '@/lib/flashcards/sm2'
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const { id: cardId } = await params
+    const body = await request.json()
+    const grade = typeof body.grade === 'number' ? body.grade : Number(body.grade)
+
+    if (!Number.isFinite(grade) || grade < 1 || grade > 4) {
+      return NextResponse.json({ error: 'Grade must be 1–4' }, { status: 400 })
+    }
+
+    const card = await prisma.flashcard.findFirst({
+      where: {
+        id: cardId,
+        deck: { userId: session.user.id },
+      },
+    })
+    if (!card) {
+      return NextResponse.json({ error: 'Card not found' }, { status: 404 })
+    }
+
+    const updated = computeSm2Update(grade, {
+      easinessFactor: card.easinessFactor,
+      interval: card.interval,
+    })
+
+    const [savedCard] = await prisma.$transaction([
+      prisma.flashcard.update({
+        where: { id: cardId },
+        data: {
+          easinessFactor: updated.easinessFactor,
+          interval: updated.interval,
+          nextReviewAt: updated.nextReviewAt,
+        },
+      }),
+      prisma.flashcardReview.create({
+        data: { cardId, grade: Math.round(grade) },
+      }),
+    ])
+
+    return NextResponse.json({
+      card: {
+        id: savedCard.id,
+        interval: savedCard.interval,
+        easinessFactor: savedCard.easinessFactor,
+        nextReviewAt: savedCard.nextReviewAt.toISOString(),
+      },
+    })
+  } catch (error) {
+    console.error('[flashcards/[id]/review]', error)
+    return NextResponse.json({ error: 'Review failed' }, { status: 500 })
+  }
+}