feat: 去掉 Judge0 依赖，SQL 改为浏览器内执行，C/C++ 改走后端 go-judge

- SQL 用 sql.js 在 Web Worker 中执行，带 5 秒超时
- C/C++ 改为请求后端 /run，请求失败时显示错误而不是一直卡在运行中
- 删除 Judge0 相关代码和 PUBLIC_JUDGE0API_URL 配置

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -26,6 +26,7 @@
     "normalize.css": "^8.0.1",
     "query-string": "^9.3.1",
     "skulpt": "^1.2.0",
+    "sql.js": "^1.15.1",
     "vue": "^3.5.34",
     "vue-codemirror": "^6.1.1"
   },
@@ -34,6 +35,7 @@
     "@rsbuild/core": "^2.0.5",
     "@rsbuild/plugin-vue": "^1.2.7",
     "@types/file-saver": "^2.0.7",
+    "@types/sql.js": "^1.4.11",
     "core-js": "^3.49.0",
     "prettier": "^3.8.3",
     "typescript": "^6.0.3"