Phase 2: learning engine — history, SRS review, mistakes, stats, exam, reminders

Answer history and schedules
- Every answer is recorded (deck, activity, topic, correct/wrong, time)
  in a versioned IndexedDB log (freezmo-learning v1, stores answers +
  srs), mirrored in memory for synchronous React reads and capped at
  20k answers (oldest pruned). StudyFeed records as it grades.
- Light SM-2 schedule per activity: 1 day, 3 days, then interval x
  ease; wrong answers return in ten minutes with the ease nudged down.

Review, mistakes, stats
- Library 'Smart review' card: due count, mistakes count (latest
  answer wrong — clears itself when answered correctly), today's goal
  progress. Review sessions freeze their item list at start.
- New /review (due across decks, ?mistakes=1 global or ?deck= per
  deck) built on a shared SessionFeed with the study feed's snap/keyboard
  mechanics, wake lock and a results slide.
- New /stats: day streak, five-week calendar, accuracy per subject and
  per deck, weakest topics (>=3 answers), daily-goal progress.
- Daily goal configurable in Settings (10/20/30/50).

Exam mode
- New /exam: pick decks, question count, optional timer; no hints
  (a NoHints context hides hint rows and the self-check escape);
  results with score, per-deck and per-topic breakdown; wrong answers
  land in the mistakes set through the normal history.

Reminders (conditional)
- VAPID-gated: GET/POST/DELETE /api/push and POST /api/push/test with
  the standard route pattern, RATE_LIMIT_PUSH, zod, auth before body.
  Subscriptions stored server-side as endpoint + keys only (PUSH_DIR).
  UI hidden entirely without keys; iOS install note; service worker
  push/notificationclick handlers; scripts/send-reminders.mjs for a
  cron/systemd timer; web-push added as the one server dependency.

Verified: new phase-2 suite 42/42 (history/SRS shapes from a real study
run, mistakes clearing, review session, stats math, exam timer and
breakdowns, VAPID-less hidden state plus the configured
subscribe/validate/test/delete path against a second instance) plus
regression 74/74, mobile 52/52, wizard 80/80, declutter 116/116,
animation 8/8, native 35/35, phase1 38/38, i18n 25/25. Key parity
709/709. Lint + build clean. SW freezmo-v26.

lib/settings.ts

@@ -22,9 +22,13 @@ export type BrowserSettings = {
   apiKey: string;
   /** Best-effort haptics on supported devices (phones). On by default. */
   haptics: boolean;
+  /** How many answers count as a finished day in the Library/stats. */
+  dailyGoal: number;
 };
 
-const EMPTY: BrowserSettings = { apiKey: "", haptics: true };
+const DEFAULT_GOAL = 20;
+
+const EMPTY: BrowserSettings = { apiKey: "", haptics: true, dailyGoal: DEFAULT_GOAL };
 
 let cached: BrowserSettings | null = null;
 const listeners = new Set<() => void>();
@@ -35,9 +39,11 @@ function read(): BrowserSettings {
     const raw = window.localStorage.getItem(STORAGE_KEY);
     if (!raw) return EMPTY;
     const parsed = JSON.parse(raw) as Partial<BrowserSettings>;
+    const goal = Number.parseInt(String(parsed.dailyGoal ?? DEFAULT_GOAL), 10);
     return {
       apiKey: typeof parsed.apiKey === "string" ? parsed.apiKey.slice(0, 512) : "",
       haptics: parsed.haptics !== false,
+      dailyGoal: Number.isFinite(goal) ? Math.min(500, Math.max(1, goal)) : DEFAULT_GOAL,
     };
   } catch {
     return EMPTY;
@@ -47,8 +53,11 @@ function read(): BrowserSettings {
 function write(next: BrowserSettings): void {
   cached = next;
   try {
-    if (next.apiKey || next.haptics === false) {
-      window.localStorage.setItem(STORAGE_KEY, JSON.stringify({ apiKey: next.apiKey, haptics: next.haptics }));
+    if (next.apiKey || next.haptics === false || next.dailyGoal !== DEFAULT_GOAL) {
+      window.localStorage.setItem(
+        STORAGE_KEY,
+        JSON.stringify({ apiKey: next.apiKey, haptics: next.haptics, dailyGoal: next.dailyGoal }),
+      );
     } else {
       window.localStorage.removeItem(STORAGE_KEY);
     }