refactor(stage8): 建表语句集中到 server/db/schema，并修复只读模式的漏写

问题
- 4 处运行时 DDL（scheduling / ele / feedback / mileage 日报）分散在路由与 store 里；
- 只读保护只按 HTTP 方法拦截，而建表由 GET 处理器触发，
  于是 DB_READ_ONLY=1 的"只读预览"仍可能执行 CREATE TABLE / ALTER TABLE（已记录在案的漏洞）。

改动
- 新增 src/server/db/schema/{guard,scheduling,ele,feedback,mileage-report}.ts：
  建表/改表的唯一位置；guard 提供 ddlAllowed()，DB_READ_ONLY=1 时每个 ensure* 直接跳过并打印一行日志。
- daily-report-store 的表名改为从 schema 模块导出，避免两处各写一份表名。
- 移除 feedback/index.ts 与 ele/migration.ts 中的内联 DDL。

验证
- 实测：DB_READ_ONLY=1 下依次调用 4 个 ensure*，全部跳过且未触碰数据库（无连接错误/挂起）。
- 架构测试新增 2 条：DDL 只允许出现在 server/db/schema；每个 schema 模块必须检查 ddlAllowed()。

lint / test(139) / build 全绿。

src/server/routes/feedback/index.ts

@@ -1,6 +1,7 @@
 import { Hono } from 'hono';
 import type { ResultSetHeader, RowDataPacket } from 'mysql2';
 import pool from '../../db/mysql.js';
+import { ensureFeedbackTable } from '../../db/schema/feedback.js';
 import type { AuthUser } from '../../auth/types.js';
 import { canManageFeedback } from '../../auth/types.js';
 import { uploadFeedbackImage } from './oss.js';
@@ -10,46 +11,6 @@ const app = new Hono();
 const MAX_IMAGE_SIZE = 5 * 1024 * 1024; // 5 MB
 const ALLOWED_MIME = new Set(['image/png', 'image/jpeg', 'image/webp', 'image/gif']);
 
-const CREATE_TABLE_SQL = `
-CREATE TABLE IF NOT EXISTS bi_user_feedback (
-  id BIGINT AUTO_INCREMENT PRIMARY KEY,
-  type ENUM('dimension','bug','ux','other') NOT NULL DEFAULT 'other',
-  module VARCHAR(64) NULL,
-  content TEXT NOT NULL,
-  contact VARCHAR(200) NULL,
-  screenshots JSON NULL,
-  user_id VARCHAR(64) NULL,
-  user_name VARCHAR(128) NULL,
-  user_agent VARCHAR(512) NULL,
-  status ENUM('open','in_progress','done','rejected') NOT NULL DEFAULT 'open',
-  reply_content TEXT NULL,
-  reply_user VARCHAR(128) NULL,
-  reply_at DATETIME NULL,
-  created_at DATETIME NOT NULL,
-  KEY idx_created_at (created_at),
-  KEY idx_type (type),
-  KEY idx_status (status),
-  KEY idx_user_id (user_id)
-) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
-`;
-
-let ensured = false;
-async function ensureTable(): Promise<void> {
-  if (ensured) return;
-  await pool.query(CREATE_TABLE_SQL);
-  // 兼容旧表：补齐缺失列
-  for (const alter of [
-    `ALTER TABLE bi_user_feedback ADD COLUMN screenshots JSON NULL AFTER contact`,
-    `ALTER TABLE bi_user_feedback ADD COLUMN reply_content TEXT NULL AFTER status`,
-    `ALTER TABLE bi_user_feedback ADD COLUMN reply_user VARCHAR(128) NULL AFTER reply_content`,
-    `ALTER TABLE bi_user_feedback ADD COLUMN reply_at DATETIME NULL AFTER reply_user`,
-    `ALTER TABLE bi_user_feedback ADD INDEX idx_user_id (user_id)`,
-  ]) {
-    try { await pool.query(alter); } catch { /* 已存在则忽略 */ }
-  }
-  ensured = true;
-}
-
 const VALID_STATUS = new Set(['open', 'in_progress', 'done', 'rejected']);
 
 const VALID_TYPES = new Set(['dimension', 'bug', 'ux', 'other']);
@@ -58,7 +19,7 @@ const VALID_TYPES = new Set(['dimension', 'bug', 'ux', 'other']);
 const CST_NOW = `DATE_ADD(UTC_TIMESTAMP(), INTERVAL 8 HOUR)`;
 
 app.post('/submit', async (c) => {
-  await ensureTable();
+  await ensureFeedbackTable();
   const body = await c.req.json().catch(() => ({})) as {
     type?: string; module?: string | null; content?: string;
     contact?: string | null; userAgent?: string; screenshots?: string[];
@@ -116,7 +77,7 @@ app.post('/upload', async (c) => {
 
 // GET /api/feedback/mine — 当前用户的反馈历史
 app.get('/mine', async (c) => {
-  await ensureTable();
+  await ensureFeedbackTable();
   const user = (c as { get?: (k: string) => unknown }).get?.('user') as AuthUser | undefined;
   if (!user?.userId) return c.json({ items: [] });
   const [rows] = await pool.query<RowDataPacket[]>(
@@ -133,7 +94,7 @@ app.get('/mine', async (c) => {
 
 // GET /api/feedback/list — 管理列表（仅 BI-ADMIN-FEEDBACK / 全量权限）
 app.get('/list', async (c) => {
-  await ensureTable();
+  await ensureFeedbackTable();
   const user = (c as { get?: (k: string) => unknown }).get?.('user') as AuthUser | undefined;
   if (!canManageFeedback(user?.roles)) {
     return c.json({ ok: false, message: '无权限' }, 403);
@@ -160,7 +121,7 @@ app.get('/list', async (c) => {
 
 // PATCH /api/feedback/:id — 管理：更新状态与回复（仅 BI-ADMIN-FEEDBACK / 全量权限）
 app.patch('/:id', async (c) => {
-  await ensureTable();
+  await ensureFeedbackTable();
   const user = (c as { get?: (k: string) => unknown }).get?.('user') as AuthUser | undefined;
   if (!canManageFeedback(user?.roles)) {
     return c.json({ ok: false, message: '无权限' }, 403);