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/lib/flashcards/sm2.ts

@@ -0,0 +1,39 @@
+export type Sm2Grade = 1 | 2 | 3 | 4
+
+export interface Sm2State {
+  easinessFactor: number
+  interval: number
+}
+
+export interface Sm2UpdateResult extends Sm2State {
+  nextReviewAt: Date
+}
+
+/** SM-2 update per US-FLASHCARDS spec (grades 1–4). */
+export function computeSm2Update(
+  grade: number,
+  previous: Sm2State,
+): Sm2UpdateResult {
+  const g = Math.min(4, Math.max(1, Math.round(grade))) as Sm2Grade
+  const ef = previous.easinessFactor
+  const newEF = Math.max(
+    1.3,
+    ef + 0.1 - (5 - g) * (0.08 + (5 - g) * 0.02),
+  )
+
+  const nextInterval =
+    g <= 2 ? 1 : Math.max(1, Math.round(previous.interval * newEF))
+
+  const nextReviewAt = new Date()
+  nextReviewAt.setDate(nextReviewAt.getDate() + nextInterval)
+
+  return {
+    easinessFactor: newEF,
+    interval: nextInterval,
+    nextReviewAt,
+  }
+}
+
+export function isCardMastered(interval: number): boolean {
+  return interval >= 21
+}