refactor: 抽取 UI 组件、改进错误页面、统一导入路径并简化数据库接口

src/server/api/routers/index.ts

@@ -1,4 +1,4 @@
-import { os } from '../server'
+import { os } from '@/server/api/server'
 import * as todo from './todo.router'
 
 export const router = os.router({

src/server/api/routers/todo.router.ts

@@ -1,8 +1,8 @@
 import { ORPCError } from '@orpc/server'
 import { eq } from 'drizzle-orm'
+import { db } from '@/server/api/middlewares'
+import { os } from '@/server/api/server'
 import { todoTable } from '@/server/db/schema'
-import { db } from '../middlewares'
-import { os } from '../server'
 
 export const list = os.todo.list.use(db).handler(async ({ context }) => {
   const todos = await context.db.query.todoTable.findMany({

src/server/db/index.ts

@@ -13,11 +13,7 @@ export type DB = ReturnType<typeof createDB>
 export const getDB = (() => {
   let db: DB | null = null
 
-  return (singleton = true): DB => {
-    if (!singleton) {
-      return createDB()
-    }
-
+  return (): DB => {
     db ??= createDB()
     return db
   }