feat(database): 添加数据库迁移支持

- 在 Cargo.toml 中添加 diesel_migrations 依赖
- 实现 run_pending_migrations 函数以运行待处理迁移
- 在 CLI 和 Web API 启动时自动运行数据库迁移

Author: DataEraserC

Cargo.lock

@@ -24,6 +24,7 @@ diesel = { version = "2.2", features = [
     "returning_clauses_for_sqlite_3_35",
     "r2d2",
 ] }
+diesel_migrations = "2.2"
 dotenvy = "0.15"
 chrono = { version = "0.4", features = ["serde"] }
 serde = { version = "1.0.219", features = ["derive"] }