fix: allow dev guest to switch to authenticated account

tests/test_dev_mode_login.py

@@ -0,0 +1,15 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+APP = (ROOT / "app" / "web_app_fastapi.py").read_text(encoding="utf-8")
+HEADER = (ROOT / "app" / "templates" / "header.html").read_text(encoding="utf-8")
+
+
+def test_dev_guest_is_allowed_to_open_login_page():
+    assert 'current_user.get("role") != "dev_guest"' in APP
+
+
+def test_dev_guest_header_offers_real_login_instead_of_logout():
+    assert "user_info.role == 'dev_guest'" in HEADER
+    assert "url_for('login')" in HEADER