feat(cli): 引入 citty CLI，迁移改为显式 ./server migrate

- 顶层新增 bin.ts 作为编译入口，citty 懒加载 src/cli/ 下子命令
- src/cli/serve.ts 通过 _serve-nitro.mjs 桥接启动 Nitro（规避
  .output/server/index.mjs 顶层 serve(...) 的副作用导入）
- src/cli/migrate.ts 显式跑 drizzle migrate；env / drizzle 都在 run()
  里 await import，避免 citty --help 遍历 subCommands 时触发 env 校验
- compile.ts 入口切到 bin.ts；移除 src/server/plugins/migrate.ts
  与 vite.config.ts 中的启动时自动迁移
- compose.yaml 新增一次性 migrate 服务，app depends_on
  service_completed_successfully，保证迁移先行再起服
- tsconfig 排除 .output / out；AGENTS.md 补充 CLI 与部署规约

bin.ts

@@ -0,0 +1,20 @@
+import { defineCommand, runMain } from 'citty'
+import { name, version } from './package.json' with { type: 'json' }
+
+// IMPORTANT: keep this file's static imports minimal. Nitro's bun preset
+// emits `.output/server/index.mjs` with a top-level `serve(...)` call, so any
+// eager (transitive) import of it would start the HTTP server even for
+// `migrate` or `--help`. All subcommands are lazy-loaded via citty.
+const main = defineCommand({
+  meta: {
+    name,
+    version,
+    description: 'Fullstack server binary (default subcommand: serve)',
+  },
+  subCommands: {
+    serve: () => import('./src/cli/serve').then((m) => m.default),
+    migrate: () => import('./src/cli/migrate').then((m) => m.default),
+  },
+})
+
+runMain(main)