chore(test): add test infrastructure, CI config, and security scanning

- Add Jenkinsfile with E2E/visual regression/security scan stages
- Add Stryker mutation testing configuration
- Add security header scanning script (check-security-headers.ts)
- Remove old playwright.config.ts (migrated to e2e/playwright.config.ts)
- Remove obsolete .claude/skills/impeccable
- Update jest config for test path patterns
- Update package.json with comprehensive test scripts
- Update .gitignore for stryker-tmp/ and .pi/ temp files

stryker.config.json

@@ -0,0 +1,51 @@
+{
+  "$schema": "./node_modules/@stryker-mutator/core/schema/stryker-schema.json",
+  "packageManager": "npm",
+  "reporters": ["html", "clear-text", "progress"],
+  "testRunner": "jest",
+  "coverageAnalysis": "perTest",
+  "mutate": [
+    "src/lib/**/*.ts",
+    "src/hooks/**/*.{ts,tsx}",
+    "src/components/ui/**/*.{ts,tsx}",
+    "src/components/layout/**/*.{ts,tsx}",
+    "src/lib/cms/**/*.ts",
+    "!src/**/*.test.{ts,tsx}",
+    "!src/**/__tests__/**",
+    "!src/lib/constants/**"
+  ],
+  "thresholds": {
+    "high": 80,
+    "low": 60,
+    "break": 30
+  },
+  "timeoutMS": 60000,
+  "cleanTempDir": true,
+  "symlinkNodeModules": true,
+  "ignorePatterns": [
+    ".eslintrc.json",
+    ".eslintrc",
+    "eslint.config.mjs",
+    ".lintstagedrc.js",
+    "commitlint.config.js",
+    "next.config.mjs",
+    "postcss.config.js",
+    "tailwind.config.js",
+    "tsconfig.json",
+    "public/",
+    "dist/",
+    ".next/",
+    "prisma/",
+    "scripts/",
+    "e2e/",
+    ".claude/",
+    ".trae/",
+    ".git/",
+    ".husky/",
+    "node_modules/",
+    "coverage/"
+  ],
+  "jest": {
+    "configFile": "config/test/jest.config.js"
+  }
+}