feat: Sprint 2 — test taking + results

Backend:
- Models: TestAttempt, AttemptAnswer (migration 002)
- POST /api/attempts: start attempt, shuffle questions/answers,
  hide is_correct, expose is_multiple for UI hints
- POST /api/attempts/{id}/submit: save answers, calculate score,
  strict matching (selected == correct), return full result
- GET /api/attempts/{id}/result: fetch saved result
- Register attempts router in main.py

Frontend:
- api/attempts.ts: types + API functions
- TestTake page: one question at a time, progress bar, timer
  with auto-submit, back navigation controlled by test setting,
  radio/checkbox based on is_multiple
- AttemptResult page: score, pass/fail, per-question breakdown
  with correct/selected/missed answer highlighting
- App.tsx: add /tests/:testId/take and /attempts/:id/result routes
- TestDetail: add "Пройти тест" button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/attempts.ts

@@ -0,0 +1,68 @@
+import client from './client'
+
+export interface AnswerForTest {
+  id: number
+  text: string
+}
+
+export interface QuestionForTest {
+  id: number
+  text: string
+  is_multiple: boolean   // true → показываем чекбоксы, false → радио-кнопки
+  answers: AnswerForTest[]
+}
+
+export interface AttemptStarted {
+  id: number
+  test_id: number
+  test_title: string
+  test_description: string | null
+  started_at: string
+  time_limit: number | null   // минуты
+  allow_navigation_back: boolean
+  questions: QuestionForTest[]
+}
+
+export interface QuestionAnswer {
+  question_id: number
+  answer_ids: number[]
+}
+
+export interface AnswerResult {
+  id: number
+  text: string
+  is_correct: boolean
+  is_selected: boolean
+}
+
+export interface QuestionResult {
+  id: number
+  text: string
+  is_answered_correctly: boolean
+  answers: AnswerResult[]
+}
+
+export interface AttemptResult {
+  id: number
+  test_id: number
+  test_title: string
+  started_at: string
+  finished_at: string
+  score: number
+  passed: boolean
+  passing_score: number
+  correct_count: number
+  total_count: number
+  questions: QuestionResult[]
+}
+
+export const attemptsApi = {
+  start: (test_id: number) =>
+    client.post<AttemptStarted>('/attempts', { test_id }),
+
+  submit: (attempt_id: number, answers: QuestionAnswer[]) =>
+    client.post<AttemptResult>(`/attempts/${attempt_id}/submit`, { answers }),
+
+  getResult: (attempt_id: number) =>
+    client.get<AttemptResult>(`/attempts/${attempt_id}/result`),
+}