chore(站内信): 消息页、后台空壳页、两个接口和 message 表一起下线

历史上一共 6 条站内信（最后一条 2025-06），发信接口两代前端都没接过，后台页面只有一句
「未完待续」，OJ2 顶栏也没有入口。

0033 是 DROP TABLE，部署要显式放行：OJ2_ALLOW_DESTRUCTIVE=1 docker/deploy.sh，
或 CI 手工触发时勾 allow_destructive。

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

packages/contract/src/content.ts

@@ -1,7 +1,6 @@
 import { z } from "zod"
 
 import { paginatedSchema, sampleUserSchema } from "./common"
-import { embeddedSubmissionSchema } from "./submission"
 
 export const announcementSchema = z.object({
   id: z.number().int(),
@@ -26,25 +25,6 @@ export const announcementListItemSchema = announcementSchema.omit({
 
 export const announcementListSchema = paginatedSchema(announcementListItemSchema)
 
-export const messageSchema = z.object({
-  id: z.number().int(),
-  sender: sampleUserSchema,
-  createTime: z.string(),
-  message: z.string(),
-  submission: embeddedSubmissionSchema,
-})
-
-export const messageListSchema = paginatedSchema(messageSchema)
-
-export const createMessageRequestSchema = z.object({
-  recipientId: z.number().int().positive(),
-  submissionId: z.string().min(1),
-  message: z
-    .string()
-    .min(1)
-    .max(1024 * 1024),
-})
-
 export const reactionKeySchema = z.enum([
   "too_easy",
   "too_hard",
@@ -194,14 +174,11 @@ export const exerciseSchema = z.object({
   solved: z.boolean(),
 })
 
-export type Message = z.infer<typeof messageSchema>
-export type MessageList = z.infer<typeof messageListSchema>
 export type Announcement = z.infer<typeof announcementSchema>
 export type AnnouncementListItem = z.infer<typeof announcementListItemSchema>
 export type TutorialSummary = z.infer<typeof tutorialSummarySchema>
 
 export type AnnouncementList = z.infer<typeof announcementListSchema>
-export type CreateMessageRequest = z.infer<typeof createMessageRequestSchema>
 export type ReactionKey = z.infer<typeof reactionKeySchema>
 export type ReactionCounts = z.infer<typeof reactionCountsSchema>
 export type ReactionState = z.infer<typeof reactionStateSchema>

packages/contract/src/submission.ts

@@ -229,24 +229,6 @@ export const submissionDetailSchema = z.object({
   caseSummary: caseSummarySchema,
 })
 
-/**
- * 内嵌在别处（目前只有站内信）的提交对象。对齐旧后端的
- * `SubmissionSafeModelSerializer(exclude=("info", "contest", "ip"))` ——
- * 这些键**根本不出现**，而不是出现但值为空。（`ip` 已随 IP 功能整体删除。）
- *
- * 独立成一个 schema 而不是复用 submissionDetailSchema 传空值：形状一致了，
- * 将来有人「顺手」把空值改成真值就不会变成泄露，因为这里压根没有这些字段。
- */
-export const embeddedSubmissionSchema = submissionDetailSchema
-  // 留下 problemDisplayId（展示用题号）而不是数字主键：站内信页面拿它拼
-  // `/problem/<题号>` 链接，给数字 id 会拼出打不开的地址。
-  .omit({
-    info: true,
-    contestId: true,
-    problemId: true,
-    caseSummary: true,
-  })
-
 /**
  * 判题进度推送。**只带前端真正要用的东西**：靠 submissionId 认领、靠 result /
  * status 决定是继续等还是去拉详情。
@@ -623,7 +605,6 @@ export type AttemptedStudent = z.infer<typeof attemptedStudentSchema>
 
 export type SubmissionListItem = z.infer<typeof submissionListItemSchema>
 export type SubmissionList = z.infer<typeof submissionListSchema>
-export type EmbeddedSubmission = z.infer<typeof embeddedSubmissionSchema>
 export type CreateSubmissionResponse = z.infer<typeof createSubmissionResponseSchema>
 export type FormatCodeResponse = z.infer<typeof formatCodeResponseSchema>