Тесты и инфраструктура

- tests/: 104 теста — lessons (все форматы ячеек), xlsx (мержи/скрытые
  столбцы/красный текст/даты), parsing (группы/недели/индексы), API (TestClient,
  TTL/modified/stale-while-error, 404/400/502)
- xlsx_builder.py: генерация xlsx в памяти для тестов без openpyxl
- docker-compose: healthz-хелскчеки (не блокируют старт), SCHEDULE_LINK
- Makefile: target test
- requirements: закреплённые версии
- .gitignore: __pycache__/, .venv/ и т.д.

docker-compose.yml

@@ -4,13 +4,14 @@ services:
       context: .
       target: api
     environment:
-      schedule_link: ${schedule_link}
+      SCHEDULE_LINK: ${SCHEDULE_LINK}
       SCHEDULE_CACHE_TTL: ${SCHEDULE_CACHE_TTL:-900}
+      SCHEDULE_RETRY_AFTER: ${SCHEDULE_RETRY_AFTER:-60}
     ports:
       - "${API_PORT:-8000}:8000"
     restart: unless-stopped
     healthcheck:
-      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8000/groups', timeout=5)"]
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8000/healthz', timeout=5)"]
       interval: 30s
       timeout: 5s
       retries: 3
@@ -29,7 +30,7 @@ services:
       api:
         condition: service_healthy
     healthcheck:
-      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8080/', timeout=5)"]
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8080/healthz', timeout=5)"]
       interval: 30s
       timeout: 5s
       retries: 3