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/src/domains/quiz/schema.ts

@@ -0,0 +1,51 @@
+import { boolean, check, index, integer, pgTable, primaryKey, text, timestamp, uniqueIndex, uuid } from 'drizzle-orm/pg-core';
+import { sql } from 'drizzle-orm';
+import { couples } from '../couples/schema.js';
+
+/**
+ * Couples quiz catalogue. `promptSelf` and `promptGuess` are two phrasings of the
+ * same question so a session can ask each partner about themselves and about the
+ * other without a second row.
+ */
+export const quizQuestions = pgTable('quiz_questions', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  promptSelf: text('prompt_self').notNull().unique(),
+  promptGuess: text('prompt_guess').notNull(),
+  options: text('options').array().notNull(),
+  sortOrder: integer('sort_order').notNull().default(0),
+  isActive: boolean('is_active').notNull().default(true),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+}, (table) => [
+  check('quiz_questions_options_length_check', sql`array_length(${table.options}, 1) between 2 and 4`),
+]);
+
+export const quizSessions = pgTable('quiz_sessions', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  coupleId: uuid('couple_id').notNull().references(() => couples.id, { onDelete: 'cascade' }),
+  status: text('status').notNull().default('active'),
+  questionIds: uuid('question_ids').array().notNull(),
+  scorePercent: integer('score_percent'),
+  completedAt: timestamp('completed_at', { withTimezone: true }),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+}, (table) => [
+  index('quiz_sessions_couple_id_created_at_idx').on(table.coupleId, table.createdAt),
+  uniqueIndex('quiz_sessions_one_active_per_couple_idx').on(table.coupleId).where(sql`${table.status} = 'active'`),
+  check('quiz_sessions_status_check', sql`${table.status} in ('active','completed')`),
+]);
+
+export const quizAnswers = pgTable('quiz_answers', {
+  sessionId: uuid('session_id').notNull().references(() => quizSessions.id, { onDelete: 'cascade' }),
+  userId: uuid('user_id').notNull(),
+  questionId: uuid('question_id').notNull(),
+  selfIndex: integer('self_index').notNull(),
+  guessIndex: integer('guess_index').notNull(),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+}, (table) => [
+  primaryKey({ columns: [table.sessionId, table.userId, table.questionId] }),
+  check('quiz_answers_self_index_check', sql`${table.selfIndex} >= 0`),
+  check('quiz_answers_guess_index_check', sql`${table.guessIndex} >= 0`),
+]);
+
+export type QuizQuestionRow = typeof quizQuestions.$inferSelect;
+export type QuizSessionRow = typeof quizSessions.$inferSelect;
+export type QuizAnswerRow = typeof quizAnswers.$inferSelect;