feat: 加固运行期可靠性并补齐调度与观测接口

- 运行句柄按 run_id 归属，修复取消后重跑时闸门被旧运行删除的竞态
- 调度循环改用取消令牌退出，启动时对账遗留运行，校验 rows_affected
- 三类任务统一参与调度，新增 /api/v1/stats 与 /api/v1/schedule
- SQLite 启用 WAL 与 busy_timeout，日志清理跳过活跃文件，单行上限 256 KiB
- 前端缓存管理令牌并在 403 时重试一次，仪表盘改用统计接口

backend/src/tasks/repository.rs

@@ -15,6 +15,38 @@ const TASK_COLUMNS: &str = "
     created_at, updated_at
 ";
 
+#[derive(Debug, Clone, Copy, Default)]
+pub struct TaskCounts {
+    pub total: u64,
+    pub enabled: u64,
+    pub script: u64,
+    pub http: u64,
+    pub process: u64,
+}
+
+/// 单条 SQL 统计全部指标，供仪表盘使用。
+pub async fn counts(pool: &SqlitePool) -> ApiResult<TaskCounts> {
+    let (total, enabled, script, http, process): (i64, i64, i64, i64, i64) = sqlx::query_as(
+        "SELECT
+            COUNT(*),
+            COALESCE(SUM(enabled), 0),
+            COALESCE(SUM(action_type = 'script'), 0),
+            COALESCE(SUM(action_type = 'http'), 0),
+            COALESCE(SUM(action_type = 'process'), 0)
+         FROM tasks",
+    )
+    .fetch_one(pool)
+    .await?;
+
+    Ok(TaskCounts {
+        total: u64::try_from(total).unwrap_or_default(),
+        enabled: u64::try_from(enabled).unwrap_or_default(),
+        script: u64::try_from(script).unwrap_or_default(),
+        http: u64::try_from(http).unwrap_or_default(),
+        process: u64::try_from(process).unwrap_or_default(),
+    })
+}
+
 pub struct ListFilters {
     pub q: Option<String>,
     pub enabled: Option<bool>,
@@ -233,14 +265,15 @@ pub async fn list(pool: &SqlitePool, filters: &ListFilters) -> ApiResult<TaskLis
     })
 }
 
-pub async fn list_enabled_script_tasks(pool: &SqlitePool) -> ApiResult<Vec<TaskResponse>> {
+/// 启动时恢复调度用的列表：所有启用任务都参与调度，不再只限脚本。
+pub async fn list_enabled_tasks(pool: &SqlitePool) -> ApiResult<Vec<TaskResponse>> {
     let rows = sqlx::query_as::<_, TaskRow>(
         "SELECT
             id, name, cron, timezone, enabled, timeout_secs, concurrency_policy,
             retry_max_attempts, retry_delay_secs, action_type, action_json,
             created_at, updated_at
         FROM tasks
-        WHERE enabled = 1 AND action_type = 'script'
+        WHERE enabled = 1
         ORDER BY updated_at DESC, id ASC",
     )
     .fetch_all(pool)