feat(deploy): migrations 嵌入二进制，实现真单文件部署

- embed-migrations.ts：扫 ./drizzle/meta/_journal.json，生成 src/server/db/migrations.gen.ts，每条 SQL 通过 `import sql_<idx> from '../../../drizzle/<tag>.sql' with { type: 'text' }` 在 bun build --compile 时被静态嵌入二进制
- migrate.ts 重写：runtime 用 createHash('sha256') 计算迁移哈希，仅用 db.execute(sql) + db.transaction() 公开 API 写入 drizzle.__drizzle_migrations 簿记表（不依赖 @internal 的 db.dialect/db.session）
- db:generate 链 db:embed，保证 SQL 改动总是同步到 migrations.gen.ts
- Dockerfile 删 COPY drizzle/，binary 是部署唯一 artifact
- 同步 README / AGENTS / biome.json

package.json

@@ -15,7 +15,8 @@
     "compile:linux:x64": "bun compile.ts --target bun-linux-x64",
     "compile:windows": "bun run compile:windows:x64",
     "compile:windows:x64": "bun compile.ts --target bun-windows-x64",
-    "db:generate": "drizzle-kit generate",
+    "db:generate": "drizzle-kit generate && bun embed-migrations.ts",
+    "db:embed": "bun embed-migrations.ts",
     "db:migrate": "drizzle-kit migrate",
     "db:push": "drizzle-kit push",
     "db:studio": "drizzle-kit studio",