feat(阶段3): oj 侧端点铺开（基线提交，未经评审）

由外部 agent (Codex) 在本会话额度中断期间完成。原样提交作为基线，
后续修复单独成 commit，便于区分与回退。

覆盖 oj 侧 65 个端点，新增 9 组路由（account/achievement/ai/classroom/
content/contest/flowchart/problemset/site）与对应 Zod 契约。

已核验：tsc --noEmit 退出码 0；API 可启动；/api/problems 返回真实数据；
judge 与 flowchart worker 均 ready。
未核验：权限边界与数据泄露，评审进行中。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/api/src/services/format-code.ts

@@ -0,0 +1,75 @@
+import { config } from "../config"
+
+export class CodeFormatError extends Error {
+  constructor(
+    message: string,
+    readonly kind: "syntax" | "tool",
+  ) {
+    super(message)
+  }
+}
+
+async function runFormatter(command: string[], code: string) {
+  let process: ReturnType<typeof Bun.spawn>
+  try {
+    process = Bun.spawn(command, {
+      stdin: new Blob([code]),
+      stdout: "pipe",
+      stderr: "pipe",
+    })
+  } catch (error) {
+    throw new CodeFormatError(String(error), "tool")
+  }
+
+  const timeout = setTimeout(() => process.kill(), 5_000)
+  const [exitCode, stdout, stderr] = await Promise.all([
+    process.exited,
+    new Response(process.stdout as ReadableStream<Uint8Array>).text(),
+    new Response(process.stderr as ReadableStream<Uint8Array>).text(),
+  ])
+  clearTimeout(timeout)
+  return { exitCode, stdout, stderr }
+}
+
+function formatSql(code: string) {
+  return code
+    .split(";")
+    .map((statement) => statement.trim())
+    .filter(Boolean)
+    .map((statement) =>
+      statement.replace(
+        /\b(select|from|where|join|left|right|inner|outer|on|group by|order by|having|limit|insert into|values|update|set|delete from|create table|drop table|alter table|and|or|as)\b/gi,
+        (keyword) => keyword.toUpperCase(),
+      ),
+    )
+    .join(";\n\n") + (code.trim().endsWith(";") ? ";" : "")
+}
+
+export async function formatCode(code: string, language: "python" | "c" | "cpp" | "sql") {
+  if (language === "sql") return formatSql(code)
+
+  if (language === "python") {
+    const result = await runFormatter(
+      [config.ruffPath, "format", "--stdin-filename", "code.py", "-"],
+      code,
+    )
+    if (result.exitCode !== 0) {
+      throw new CodeFormatError(result.stderr || "Invalid Python syntax", "syntax")
+    }
+    return result.stdout
+  }
+
+  const filename = language === "c" ? "code.c" : "code.cpp"
+  const result = await runFormatter(
+    [
+      config.clangFormatPath,
+      `-assume-filename=${filename}`,
+      "-style={BasedOnStyle: LLVM, IndentWidth: 4, BreakBeforeBraces: Attach}",
+    ],
+    code,
+  )
+  if (result.exitCode !== 0) {
+    throw new CodeFormatError(result.stderr || "Formatting failed", "tool")
+  }
+  return result.stdout
+}