feat(quiz): couples quiz with shareable watermarked results card

Replaces the notify-me quiz stub with a full loop: quiz sessions per
couple, answer-and-guess flow, dual-direction scoring, and a score-only
share card (no question or answer content) captured via ViewShot with
Sauci branding.

API: migration 0019 (quiz_questions, quiz_sessions, quiz_answers, 12
seeded questions), new quiz domain with session start / current /
answers / result routes, couple isolation, route + integration +
scoring unit tests.

Mobile: src/features/quiz feature (intro, per-question self+guess flow,
waiting-for-partner nudge, results with breakdown), quizStore with
sign-out clearing, QuizShareModal following SharePreviewModal, discovery
QuizTile, analytics events, and tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/api/test/quiz.integration.test.ts

@@ -0,0 +1,209 @@
+import { randomUUID } from 'node:crypto';
+import { readdir, readFile } from 'node:fs/promises';
+import { Pool } from 'pg';
+import { afterAll, beforeAll, beforeEach, describe, expect, it } from 'vitest';
+import { PostgresQuizRepository } from '../src/domains/quiz/repository.js';
+
+const url = process.env.DATABASE_URL;
+const local = url ? ['127.0.0.1', 'localhost', '::1'].includes(new URL(url).hostname) : false;
+if (url && !local) throw new Error('Quiz integration tests only permit localhost');
+
+describe.skipIf(!url || !local)('quiz + PostgreSQL', () => {
+  const admin = new Pool({ connectionString: url });
+  const schema = `quiz_${randomUUID().replaceAll('-', '')}`;
+  let pool: Pool;
+  let repo: PostgresQuizRepository;
+
+  const userA = '11111111-1111-4111-8111-111111111111';
+  const userB = '22222222-2222-4222-8222-222222222222';
+  const soloUser = '33333333-3333-4333-8333-333333333333';
+  const outsider = '44444444-4444-4444-8444-444444444444';
+  const couple = '55555555-5555-4555-8555-555555555555';
+  const soloCouple = '66666666-6666-4666-8666-666666666666';
+  const otherCouple = '77777777-7777-4777-8777-777777777777';
+
+  beforeAll(async () => {
+    await admin.query(`create schema "${schema}"`);
+    const isolated = new URL(url!);
+    isolated.searchParams.set('options', `-c search_path=${schema}`);
+    pool = new Pool({ connectionString: isolated.toString() });
+    repo = new PostgresQuizRepository(isolated.toString());
+
+    const dir = new URL('../drizzle/', import.meta.url);
+    const files = (await readdir(dir)).filter((name) => name.endsWith('.sql')).sort();
+    for (const name of files) {
+      const sql = await readFile(new URL(name, dir), 'utf8');
+      for (const statement of sql.split('--> statement-breakpoint')) {
+        if (statement.trim()) await pool.query(statement);
+      }
+    }
+
+    await pool.query(
+      'insert into couples(id,invite_code) values($1,$2),($3,$4),($5,$6)',
+      [couple, 'QUIZAAA1', soloCouple, 'QUIZAAA2', otherCouple, 'QUIZAAA3'],
+    );
+    await pool.query(
+      `insert into profiles(id,couple_id) values
+        ($1,$5),($2,$5),($3,$6),($4,$7)`,
+      [userA, userB, soloUser, outsider, couple, soloCouple, otherCouple],
+    );
+  });
+
+  beforeEach(async () => {
+    await pool.query('delete from quiz_answers');
+    await pool.query('delete from quiz_sessions');
+  });
+
+  afterAll(async () => {
+    await repo.close();
+    await pool.end();
+    await admin.query(`drop schema "${schema}" cascade`);
+    await admin.end();
+  });
+
+  it('refuses to start a quiz without a couple or without a partner', async () => {
+    await expect(repo.startSession(randomUUID())).rejects.toMatchObject({ code: 'no_couple' });
+    await expect(repo.startSession(soloUser)).rejects.toMatchObject({ code: 'partner_required' });
+  });
+
+  it('starts a session with ten active questions and returns it idempotently', async () => {
+    const first = await repo.startSession(userA);
+    expect(first.created).toBe(true);
+    expect(first.session.status).toBe('active');
+    expect(first.session.questions).toHaveLength(10);
+    expect(first.session.score_percent).toBeNull();
+    expect(first.session.my_answers).toEqual([]);
+    expect(first.session.i_completed).toBe(false);
+    expect(first.session.partner_completed).toBe(false);
+
+    const second = await repo.startSession(userA);
+    expect(second.created).toBe(false);
+    expect(second.session.id).toBe(first.session.id);
+
+    // The partner starting also resolves to the same active session.
+    const partnerView = await repo.startSession(userB);
+    expect(partnerView.created).toBe(false);
+    expect(partnerView.session.id).toBe(first.session.id);
+  });
+
+  it('walks the full happy path: both partners answer, session completes, score is exact', async () => {
+    const { session } = await repo.startSession(userA);
+    const questionIds = session.questions.map((question) => question.id);
+    expect(questionIds).toHaveLength(10);
+
+    // Self-answers alternate 0/1 per question so a guess cannot accidentally match
+    // by coincidence. A guesses B's self-answer correctly on the first 6 questions
+    // and wrong on the rest; B guesses A's self-answer correctly on the first 3
+    // questions and wrong on the rest.
+    const bSelf = questionIds.map((_, index) => index % 2);
+    const aSelf = questionIds.map((_, index) => 1 - (index % 2));
+    const aGuess = bSelf.map((value, index) => (index < 6 ? value : 1 - value));
+    const bGuess = aSelf.map((value, index) => (index < 3 ? value : 1 - value));
+
+    const aAnswers = questionIds.map((questionId, index) => ({
+      question_id: questionId,
+      self_index: aSelf[index]!,
+      guess_index: aGuess[index]!,
+    }));
+    const bAnswers = questionIds.map((questionId, index) => ({
+      question_id: questionId,
+      self_index: bSelf[index]!,
+      guess_index: bGuess[index]!,
+    }));
+
+    const afterA = await repo.submitAnswers(userA, session.id, aAnswers);
+    expect(afterA.status).toBe('active');
+    expect(afterA.i_completed).toBe(true);
+    expect(afterA.partner_completed).toBe(false);
+    expect(afterA.my_answers).toHaveLength(10);
+
+    const afterB = await repo.submitAnswers(userB, session.id, bAnswers);
+    expect(afterB.status).toBe('completed');
+    expect(afterB.completed_at).not.toBeNull();
+    expect(afterB.i_completed).toBe(true);
+    expect(afterB.partner_completed).toBe(true);
+
+    // A guessed right (guess=1 matches B's self=1) on questions 0-5: 6 hits.
+    // B guessed right (guess=0 matches A's self=0) on questions 0-2: 3 hits.
+    // Total 9 hits out of 20 possible = 45%.
+    expect(afterB.score_percent).toBe(45);
+
+    const result = await repo.result(userA, session.id);
+    expect(result.score_percent).toBe(45);
+    expect(result.completed_at).not.toBeNull();
+    expect(result.questions).toHaveLength(10);
+    expect(result.questions[0]).toMatchObject({
+      my_self_index: aSelf[0],
+      my_guess_index: aGuess[0],
+      partner_self_index: bSelf[0],
+      partner_guess_index: bGuess[0],
+      i_guessed_right: true,
+      partner_guessed_right: true,
+    });
+    expect(result.questions[9]).toMatchObject({
+      i_guessed_right: false,
+      partner_guessed_right: false,
+    });
+
+    // The partner's result view mirrors the same score with roles swapped.
+    const partnerResult = await repo.result(userB, session.id);
+    expect(partnerResult.score_percent).toBe(45);
+  });
+
+  it('rejects an incomplete or mismatched answer set', async () => {
+    const { session } = await repo.startSession(userA);
+    const questionIds = session.questions.map((question) => question.id);
+
+    await expect(
+      repo.submitAnswers(userA, session.id, [
+        { question_id: questionIds[0]!, self_index: 0, guess_index: 0 },
+      ]),
+    ).rejects.toMatchObject({ code: 'invalid_answers' });
+
+    await expect(
+      repo.submitAnswers(userA, session.id, [
+        ...questionIds.map((id) => ({ question_id: id, self_index: 0, guess_index: 0 })),
+        { question_id: randomUUID(), self_index: 0, guess_index: 0 },
+      ]),
+    ).rejects.toMatchObject({ code: 'invalid_answers' });
+
+    const options = session.questions[0]!.options;
+    await expect(
+      repo.submitAnswers(userA, session.id, questionIds.map((id) => ({
+        question_id: id,
+        self_index: options.length,
+        guess_index: 0,
+      }))),
+    ).rejects.toMatchObject({ code: 'invalid_answers' });
+  });
+
+  it('isolates sessions to their own couple', async () => {
+    const { session } = await repo.startSession(userA);
+    await expect(repo.submitAnswers(outsider, session.id, [])).rejects.toMatchObject({ code: 'session_not_found' });
+    await expect(repo.result(outsider, session.id)).rejects.toMatchObject({ code: 'session_not_found' });
+    expect(await repo.currentSession(outsider)).toBeNull();
+  });
+
+  it('blocks the answers endpoint once the session has completed', async () => {
+    const { session } = await repo.startSession(userA);
+    const questionIds = session.questions.map((question) => question.id);
+    const answers = questionIds.map((id) => ({ question_id: id, self_index: 0, guess_index: 0 }));
+    await repo.submitAnswers(userA, session.id, answers);
+    const completed = await repo.submitAnswers(userB, session.id, answers);
+    expect(completed.status).toBe('completed');
+
+    await expect(repo.submitAnswers(userA, session.id, answers)).rejects.toMatchObject({ code: 'session_completed' });
+  });
+
+  it('blocks the result endpoint before the session has completed', async () => {
+    const { session } = await repo.startSession(userA);
+    await expect(repo.result(userA, session.id)).rejects.toMatchObject({ code: 'session_not_completed' });
+  });
+
+  it('returns the couple\'s most recent session from currentSession', async () => {
+    expect(await repo.currentSession(userA)).toBeNull();
+    const { session } = await repo.startSession(userA);
+    const current = await repo.currentSession(userB);
+    expect(current?.id).toBe(session.id);
+  });
+});