feat: prompt users to start Telegram bot for notifications

tests/test_telegram_notifications.py

@@ -0,0 +1,24 @@
+from types import SimpleNamespace
+
+from bot.services.telegram_notifications import telegram_notifications_need_prompt
+
+
+def _user(status: str):
+    return SimpleNamespace(telegram_id=123, telegram_notifications_status=status)
+
+
+def test_telegram_notifications_prompt_only_for_explicit_unreachable_statuses():
+    assert telegram_notifications_need_prompt(_user("needs_start")) is True
+    assert telegram_notifications_need_prompt(_user("blocked")) is True
+    assert telegram_notifications_need_prompt(_user("enabled")) is False
+    assert telegram_notifications_need_prompt(_user("unknown")) is False
+
+
+def test_telegram_notifications_prompt_requires_linked_telegram():
+    user = SimpleNamespace(
+        email="user@example.test",
+        telegram_id=None,
+        telegram_notifications_status="needs_start",
+    )
+
+    assert telegram_notifications_need_prompt(user) is False