新增: 依赖图环形检测 + PNG 导出 + 任务列表真实总数

- 后端 detect_module_cycles IPC(DFS 三色标记法检测环形依赖)
- 前端环检测按钮:高亮参与环的节点(红色边框)
- 图导出 PNG(X6 toPNG 回调模式)
- 后端 count_tasks IPC + 前端 taskApi.count()
- 任务列表所有筛选/搜索/排序/翻页均拉真实 total

src-tauri/src/commands/module.rs

@@ -1198,3 +1198,72 @@ pub async fn list_module_dependencies(
         .await
         .map_err(err_str)
 }
+
+/// 检测工程依赖图中的环形依赖(DFS 三色标记法)。
+/// 返回参与环的 module_id 列表(空 = 无环)。
+#[tauri::command]
+pub async fn detect_module_cycles(
+    state: State<'_, AppState>,
+    project_id: String,
+) -> Result<Vec<String>, String> {
+    let project_id = project_id.trim().to_string();
+    if project_id.is_empty() {
+        return Err("project_id 不能为空".to_string());
+    }
+    let deps = state
+        .module_dependencies
+        .list_by_field("project_id", &project_id)
+        .await
+        .map_err(err_str)?;
+    // 构建邻接表
+    let mut adj: std::collections::HashMap<String, Vec<String>> = std::collections::HashMap::new();
+    for d in &deps {
+        adj.entry(d.from_module_id.clone())
+            .or_default()
+            .push(d.to_module_id.clone());
+        adj.entry(d.to_module_id.clone()).or_default();
+    }
+    // DFS 三色:0=白(未访问) 1=灰(栈中) 2=黑(完成)
+    let mut color: std::collections::HashMap<String, u8> = std::collections::HashMap::new();
+    let mut cycle_nodes: std::collections::HashSet<String> = std::collections::HashSet::new();
+    fn dfs(
+        node: &str,
+        adj: &std::collections::HashMap<String, Vec<String>>,
+        color: &mut std::collections::HashMap<String, u8>,
+        cycle_nodes: &mut std::collections::HashSet<String>,
+        path: &mut Vec<String>,
+    ) {
+        let c = color.get(node).copied().unwrap_or(0);
+        if c == 1 {
+            // 发现环:path 中从当前节点开始的都参与环
+            let in_cycle = path.iter().position(|n| n == node);
+            if let Some(start) = in_cycle {
+                for n in &path[start..] {
+                    cycle_nodes.insert(n.clone());
+                }
+            }
+            cycle_nodes.insert(node.to_string());
+            return;
+        }
+        if c == 2 {
+            return;
+        }
+        color.insert(node.to_string(), 1);
+        path.push(node.to_string());
+        if let Some(neighbors) = adj.get(node) {
+            for next in neighbors {
+                dfs(next, adj, color, cycle_nodes, path);
+            }
+        }
+        path.pop();
+        color.insert(node.to_string(), 2);
+    }
+    let nodes: Vec<String> = adj.keys().cloned().collect();
+    let mut path: Vec<String> = Vec::new();
+    for n in &nodes {
+        if color.get(n).copied().unwrap_or(0) == 0 {
+            dfs(n, &adj, &mut color, &mut cycle_nodes, &mut path);
+        }
+    }
+    Ok(cycle_nodes.into_iter().collect())
+}

src-tauri/src/commands/task.rs

@@ -203,6 +203,16 @@ pub async fn list_tasks(
     Ok(tasks)
 }
 
+/// 按条件计数任务(分页 total 用)。
+#[tauri::command]
+pub async fn count_tasks(
+    state: State<'_, AppState>,
+    query: Option<TaskQuery>,
+) -> Result<i64, String> {
+    let q = query.unwrap_or_default();
+    state.tasks.count_by_query(&q).await.map_err(err_str)
+}
+
 /// 按 id 查任务，找不到返回 Err(供前端详情页)
 #[tauri::command]
 pub async fn get_task_by_id(

src-tauri/src/lib.rs

@@ -300,6 +300,7 @@ pub fn run() {
             commands::project::import_projects_batch,
             // 任务
             commands::task::list_tasks,
+            commands::task::count_tasks,
             commands::task::create_task,
             commands::task::update_task,
             commands::task::delete_task,
@@ -337,6 +338,7 @@ pub fn run() {
             commands::module::add_module_dependency,
             commands::module::remove_module_dependency,
             commands::module::list_module_dependencies,
+            commands::module::detect_module_cycles,
             // 灵感
             commands::idea::list_ideas,
             commands::idea::create_idea,