Add security standards and CI infrastructure

- SECURITY.md with vulnerability disclosure policy and self-hosting guidance
- Dependabot config for weekly dependency updates (npm, Docker, Actions)
- ESLint v9 flat config for frontend and backend, with eslint-plugin-security
- GitHub Actions CI: lint, typecheck, build, and npm audit on every push/PR
- CodeQL workflow for automated security scanning (runs on push and weekly)

frontend/package.json

@@ -7,7 +7,7 @@
     "dev": "vite",
     "build": "tsc && vite build",
     "preview": "vite preview",
-    "lint": "eslint src --ext .ts,.tsx"
+    "lint": "eslint src"
   },
   "dependencies": {
     "@tanstack/react-query": "^5.17.1",
@@ -29,13 +29,19 @@
     "zustand": "^4.4.7"
   },
   "devDependencies": {
+    "@eslint/js": "^9.39.4",
     "@types/react": "^18.2.48",
     "@types/react-dom": "^18.2.18",
     "@vitejs/plugin-react": "^4.2.1",
     "autoprefixer": "^10.4.17",
+    "eslint": "^9.39.4",
+    "eslint-plugin-react": "^7.37.5",
+    "eslint-plugin-react-hooks": "^7.0.1",
+    "eslint-plugin-security": "^4.0.0",
     "postcss": "^8.4.33",
     "tailwindcss": "^3.4.1",
     "typescript": "^5.3.3",
+    "typescript-eslint": "^8.58.2",
     "vite": "^5.0.11"
   }
 }