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/profile.ts

@@ -0,0 +1,41 @@
+import { sessionUserSchema, userProfileSchema } from "@oj2/contract"
+import { and, eq } from "drizzle-orm"
+
+import { db, schema } from "../db"
+
+export async function getUserProfileById(userId: number, showRealName: boolean) {
+  const [row] = await db
+    .select({ profile: schema.userProfile, user: schema.user })
+    .from(schema.userProfile)
+    .innerJoin(schema.user, eq(schema.userProfile.userId, schema.user.id))
+    .where(and(eq(schema.user.id, userId), eq(schema.user.isDisabled, false)))
+    .limit(1)
+
+  if (!row) return null
+  return userProfileSchema.parse({
+    id: row.profile.id,
+    user: sessionUserSchema.parse({
+      id: row.user.id,
+      username: row.user.username,
+      email: row.user.email,
+      adminType: row.user.adminType,
+      problemPermission: row.user.problemPermission,
+      createTime: row.user.createTime,
+      lastLogin: row.user.lastLogin,
+      openApi: row.user.openApi,
+      isDisabled: row.user.isDisabled,
+      className: row.user.className,
+    }),
+    realName: showRealName ? row.profile.realName : null,
+    acmProblemsStatus: row.profile.acmProblemsStatus,
+    avatar: row.profile.avatar,
+    blog: row.profile.blog,
+    mood: row.profile.mood,
+    github: row.profile.github,
+    school: row.profile.school,
+    major: row.profile.major,
+    language: row.profile.language,
+    acceptedNumber: row.profile.acceptedNumber,
+    submissionNumber: row.profile.submissionNumber,
+  })
+}