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-lock.json

@@ -24,6 +24,7 @@
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         "skulpt": "^1.2.0",
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@@ -32,6 +33,7 @@
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+        "@types/sql.js": "^1.4.11",
         "core-js": "^3.49.0",
         "prettier": "^3.8.3",
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@@ -220,9 +222,9 @@
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       "license": "MIT",
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@@ -634,6 +636,13 @@
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@@ -656,6 +665,27 @@
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@@ -1539,6 +1569,12 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
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+    "node_modules/sql.js": {
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+      "resolved": "https://registry.npmjs.org/sql.js/-/sql.js-1.15.1.tgz",
+      "integrity": "sha512-i0M/6s+lcl67Flm/1m8/AeVU5caDramlILXU/udUwpTQym2qKMSe2sJiXB5d5WXFB272aj4B2v1JbtQ93ID3Pg==",
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@@ -1586,6 +1622,13 @@
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