Enhance test jobs with caching, coverage, and parallel execution

CI improvements:
- Add needs: [] to run tests parallel with build (faster pipeline)
- Add pip/npm caching (faster subsequent runs)
- Add 15m timeout to prevent hung jobs
- Add pytest coverage with cobertura report for GitLab
- Add pytest JUnit report for test tab in MR
- Add vitest coverage with cobertura report for GitLab
- Add coverage regex for badge display

Frontend:
- Add @vitest/coverage-v8 dependency
- Configure vitest coverage reporter (text, cobertura, html)

frontend/package.json

@@ -23,6 +23,7 @@
     "@types/react": "^18.2.48",
     "@types/react-dom": "^18.2.18",
     "@vitejs/plugin-react": "^4.2.1",
+    "@vitest/coverage-v8": "^1.3.1",
     "jsdom": "^24.0.0",
     "typescript": "^5.3.3",
     "vite": "^5.0.12",

frontend/vite.config.ts

@@ -16,5 +16,10 @@ export default defineConfig({
     environment: 'jsdom',
     setupFiles: './src/test/setup.ts',
     css: true,
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'cobertura', 'html'],
+      reportsDirectory: './coverage',
+    },
   }
 })