chore: 加 oxlint，现存 19 条 warning 清零

原来只有 Prettier，没有任何 lint。根目录加 `bun run lint`（oxlint，覆盖后端、前端、
契约，--deny-warnings：有一条就算失败），CLAUDE.md 常用检查里加上。

现存 19 条顺手清掉：
- 11 处未使用的 import / catch 参数 / 回调参数
- oj/store/problem.ts：`...problem.value?.languages` 展开可能是 undefined
  （外层 if 已经保证非空，去掉 ?.）
- admin/problem/detail.vue：`contestId = contestId` 自赋值，删掉
- judge/sql/engine.ts：注释里的 `/*x*/` 示例原来靠零宽空格防止提前闭合注释，
  改成 `*\/`
- 其余：多余的 !!、new Array(n)、展开里多余的 `|| {}`

两边类型检查、前端构建、后端单二进制编译都过。

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

apps/api/src/db/schema.ts

@@ -755,7 +755,7 @@ export const problemTag = pgTable(
     id: serial().primaryKey().notNull(),
     name: text().notNull(),
   },
-  (table) => [
+  () => [
     uniqueIndex("problem_tag_name_ci_unique").using("btree", sql`lower(name)`),
   ],
 )

apps/api/src/judge/sql/engine.ts

@@ -159,7 +159,7 @@ function iterate(db: Database, script: string): Iterable<PreparedStatement> {
 
 /**
  * 取语句的首关键字。优先用 sqlite3_normalized_sql —— 归一化由 SQLite 自己做，
- * 注释、大小写、空白都已抹平（`/*x*​/ pragma  Query_Only = 0` → `PRAGMA query_only=?`），
+ * 注释、大小写、空白都已抹平（`/*x*\/ pragma  Query_Only = 0` → `PRAGMA query_only=?`），
  * 比在原文上自己做词法猜测可靠得多。
  */
 function leadingKeyword(statement: PreparedStatement) {

apps/api/src/routes/account.ts

@@ -2,7 +2,6 @@ import { randomBytes } from "node:crypto"
 import { resolve } from "node:path"
 
 import {
-  rankProfileSchema,
   registerRequestSchema,
   STUDENT_ROLES,
   updateProfileRequestSchema,

apps/api/src/routes/admin/contest.ts

@@ -14,7 +14,7 @@ import type { AuthUser } from "../../auth/session"
 import { db, schema } from "../../db"
 import { failure, parseBody, success } from "../../http"
 import { contestStatus } from "../../services/contest"
-import { objectValue, queryInteger, sampleUser } from "../helpers"
+import { queryInteger, sampleUser } from "../helpers"
 
 export const adminContestRoutes = new Hono<AppEnv>()
 

apps/api/src/routes/content.ts

@@ -1,6 +1,5 @@
 import {
   createMessageRequestSchema,
-  embeddedSubmissionSchema,
   exerciseAttemptRequestSchema,
   reactionKeySchema,
   setReactionRequestSchema,

apps/api/src/routes/flowchart.ts

@@ -147,7 +147,7 @@ flowchartRoutes.post("/flowcharts", requireAuth, async (c) => {
   })
   try {
     await flowchartQueue.add("evaluate", { submissionId: id }, { jobId: id })
-  } catch (error) {
+  } catch {
     await db
       .update(schema.flowchartSubmission)
       .set({ status: 3 })
@@ -642,7 +642,7 @@ flowchartRoutes.post("/flowcharts/:id/retry", requireAuth, async (c) => {
       { submissionId: row.flowchart.id },
       { jobId: `${row.flowchart.id}:retry:${Date.now()}` },
     )
-  } catch (error) {
+  } catch {
     // 入队失败就落 FAILED，别把提交丢在 PENDING 上 —— 和 POST /flowcharts 同一处理
     await db
       .update(schema.flowchartSubmission)

apps/api/src/routes/submission-statistics.ts

@@ -26,7 +26,6 @@ import {
 import { Hono } from "hono"
 
 import { optionalAuth, requireTeacher } from "../auth/middleware"
-import type { AuthUser } from "../auth/session"
 import { db, schema } from "../db"
 import { failure, success } from "../http"
 import {