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

vitest.config.ts

@@ -0,0 +1,21 @@
+/** @type {import('vite').UserConfig} */
+export default {
+  test: {
+    globals: true,
+    environment: 'jsdom',
+    include: ['src/**/*.spec.ts'],
+    setupFiles: ['src/test-setup.ts'],
+    reporters: ['default', 'html'],
+    coverage: {
+      enabled: true,
+      reportsDirectory: 'coverage/frontend',
+      reporter: ['text', 'html', 'lcov'],
+      thresholds: {
+        lines: 0,
+        branches: 0,
+        functions: 0,
+        statements: 0,
+      },
+    },
+  },
+};