feat: add test framework, unit tests, and GitLab CI pipeline

- Add pytest config in backend/pyproject.toml with asyncio mode and coverage
- Add backend/requirements-test.txt with pytest, pytest-cov, pytest-asyncio, aiosqlite
- Write 86 backend unit tests covering auth (JWT tokens), schemas (Pydantic
  models), config (Settings env overrides), log_parser (log parsing, IP
  resolution, geo data), models (SQLAlchemy table definitions + column
  defaults), and theme export
- Add Vitest config for Angular frontend (vitest.config.ts, src/test-setup.ts)
- Add .gitlab-ci.yml with stages: backend-test, frontend-test, backend-lint,
  docker-build, and quality-gate
- CI enforces 10% minimum coverage threshold for backend

backend/tests/test_theme_export.py

@@ -0,0 +1,22 @@
+"""Tests for theme_export — theme.json generation from station config."""
+
+import os
+import json
+import pytest
+from unittest.mock import patch, AsyncMock, MagicMock
+
+from app.config import Settings
+
+
+class TestThemeExport:
+    """Tests for theme.json export logic."""
+
+    def test_settings_theme_json_path_default(self):
+        with patch.dict("os.environ", {"KMTN_THEME_JSON_PATH": "/app/theme.json"}, clear=False):
+            settings = Settings()
+            assert settings.THEME_JSON_PATH == "/app/theme.json"
+
+    def test_settings_website_url_default(self):
+        with patch.dict("os.environ", {"KMTN_WEBSITE_URL": "https://kmountainflower.org"}, clear=False):
+            settings = Settings()
+            assert settings.WEBSITE_URL == "https://kmountainflower.org"