refactor(saas): 架构重构 + 性能优化 — 借鉴 loco-rs 模式

Phase 0: 知识库
- docs/knowledge-base/loco-rs-patterns.md — loco-rs 10 个可借鉴模式研究

Phase 1: 数据层重构
- crates/zclaw-saas/src/models/ — 15 个 FromRow 类型化模型
- Login 3 次查询合并为 1 次 AccountLoginRow 查询
- 所有 service 文件从元组解构迁移到 FromRow 结构体

Phase 2: Worker + Scheduler 系统
- crates/zclaw-saas/src/workers/ — Worker trait + 5 个具体实现
- crates/zclaw-saas/src/scheduler.rs — TOML 声明式调度器
- crates/zclaw-saas/src/tasks/ — CLI 任务系统

Phase 3: 性能修复
- Relay N+1 查询 → 精准 SQL (relay/handlers.rs)
- Config RwLock → AtomicU32 无锁 rate limit (state.rs, middleware.rs)
- SSE std::sync::Mutex → tokio::sync::Mutex (relay/service.rs)
- /auth/refresh 阻塞清理 → Scheduler 定期执行

Phase 4: 多环境配置
- config/saas-{development,production,test}.toml
- ZCLAW_ENV 环境选择 + ZCLAW_SAAS_CONFIG 精确覆盖
- scheduler 配置集成到 TOML

crates/zclaw-saas/src/config.rs

@@ -14,6 +14,37 @@ pub struct SaaSConfig {
     pub relay: RelayConfig,
     #[serde(default)]
     pub rate_limit: RateLimitConfig,
+    #[serde(default)]
+    pub scheduler: SchedulerConfig,
+}
+
+/// Scheduler 定时任务配置
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SchedulerConfig {
+    #[serde(default)]
+    pub jobs: Vec<JobConfig>,
+}
+
+/// 单个定时任务配置
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JobConfig {
+    pub name: String,
+    /// 间隔时间，支持 "5m", "1h", "24h", "30s" 格式
+    pub interval: String,
+    /// 对应的 Worker 名称
+    pub task: String,
+    /// 传递给 Worker 的参数（JSON 格式）
+    #[serde(default)]
+    pub args: Option<serde_json::Value>,
+    /// 是否在启动时立即执行
+    #[serde(default)]
+    pub run_on_start: bool,
+}
+
+impl Default for SchedulerConfig {
+    fn default() -> Self {
+        Self { jobs: Vec::new() }
+    }
 }
 
 /// 服务器配置
@@ -51,8 +82,10 @@ pub struct AuthConfig {
 pub struct RelayConfig {
     #[serde(default = "default_max_queue")]
     pub max_queue_size: usize,
+    // TODO: implement per-provider concurrency limiting
     #[serde(default = "default_max_concurrent")]
     pub max_concurrent_per_provider: usize,
+    // TODO: implement batch window
     #[serde(default = "default_batch_window")]
     pub batch_window_ms: u64,
     #[serde(default = "default_retry_delay")]
@@ -104,6 +137,7 @@ impl Default for SaaSConfig {
             auth: AuthConfig::default(),
             relay: RelayConfig::default(),
             rate_limit: RateLimitConfig::default(),
+            scheduler: SchedulerConfig::default(),
         }
     }
 }
@@ -147,11 +181,31 @@ impl Default for RelayConfig {
 }
 
 impl SaaSConfig {
-    /// 加载配置文件，优先级: 环境变量 > ZCLAW_SAAS_CONFIG > ./saas-config.toml
+    /// 加载配置文件，优先级: ZCLAW_SAAS_CONFIG > ZCLAW_ENV > ./saas-config.toml
+    ///
+    /// ZCLAW_ENV 环境选择:
+    ///   development → config/saas-development.toml
+    ///   production  → config/saas-production.toml
+    ///   test        → config/saas-test.toml
+    ///
+    /// ZCLAW_SAAS_CONFIG 指定精确路径（最高优先级）
     pub fn load() -> anyhow::Result<Self> {
-        let config_path = std::env::var("ZCLAW_SAAS_CONFIG")
-            .map(PathBuf::from)
-            .unwrap_or_else(|_| PathBuf::from("saas-config.toml"));
+        let config_path = if let Ok(path) = std::env::var("ZCLAW_SAAS_CONFIG") {
+            PathBuf::from(path)
+        } else if let Ok(env) = std::env::var("ZCLAW_ENV") {
+            let filename = format!("config/saas-{}.toml", env);
+            let path = PathBuf::from(&filename);
+            if !path.exists() {
+                anyhow::bail!(
+                    "ZCLAW_ENV={} 指定的配置文件 {} 不存在",
+                    env, filename
+                );
+            }
+            tracing::info!("Loading config for environment: {}", env);
+            path
+        } else {
+            PathBuf::from("saas-config.toml")
+        };
 
         let mut config = if config_path.exists() {
             let content = std::fs::read_to_string(&config_path)?;