refactor: 合并为单 crate，前端改为内嵌 React 控制台

合并 stash-cli / stash-core 为根目录单 crate（lib + bin），新增 React + Vite + TS 控制台替换 Askama 模板。
build.rs 用 walkdir 把 stash-web/dist 同步到 $OUT_DIR/web，由 include_dir! 编译期内嵌，产出单文件二进制。
路由改为 / 与 /assets/** 走内嵌前端，其余交给 ServeDir，缺失路径返回内置 404。同步更新依赖、.gitignore 与 README。

src/watcher.rs

@@ -0,0 +1,122 @@
+use crate::{AppProject, error::StashError, scan_projects};
+use notify::{Event, EventKind, RecursiveMode, Watcher};
+use std::{path::PathBuf, time::Duration};
+use tokio::sync::{broadcast, mpsc};
+use tracing::warn;
+
+const EVENT_DEBOUNCE: Duration = Duration::from_millis(150);
+
+pub fn start(root: PathBuf, updates: broadcast::Sender<Vec<AppProject>>) -> Result<(), StashError> {
+    let mut previous_projects = scan_projects(&root);
+    let (event_tx, mut event_rx) = mpsc::unbounded_channel();
+    let mut watcher = notify::recommended_watcher(move |result| {
+        let _ = event_tx.send(result);
+    })?;
+    watcher.watch(&root, RecursiveMode::Recursive)?;
+
+    tokio::spawn(async move {
+        let _watcher = watcher;
+
+        while let Some(event) = event_rx.recv().await {
+            if !should_rescan(&event) {
+                continue;
+            }
+
+            // Editors and build tools often emit a burst of file events for one change.
+            tokio::time::sleep(EVENT_DEBOUNCE).await;
+            while event_rx.try_recv().is_ok() {}
+
+            let projects = scan_projects(&root);
+            if projects == previous_projects {
+                continue;
+            }
+
+            previous_projects = projects.clone();
+            let _ = updates.send(projects);
+        }
+    });
+
+    Ok(())
+}
+
+fn should_rescan(event: &notify::Result<Event>) -> bool {
+    match event {
+        Ok(event) => !matches!(event.kind, EventKind::Access(_)),
+        Err(error) => {
+            warn!("文件监听事件出错，将重新扫描项目: {error}");
+            true
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use notify::{
+        Event,
+        event::{AccessKind, CreateKind, EventKind},
+    };
+    use std::{
+        fs,
+        path::{Path, PathBuf},
+        sync::atomic::{AtomicU64, Ordering},
+        time::Duration,
+    };
+
+    static NEXT_TEMP_ID: AtomicU64 = AtomicU64::new(0);
+
+    struct TestDir {
+        path: PathBuf,
+    }
+
+    impl TestDir {
+        fn new() -> Self {
+            let id = NEXT_TEMP_ID.fetch_add(1, Ordering::Relaxed);
+            let path = std::env::temp_dir()
+                .join(format!("stash-watcher-test-{}-{id}", std::process::id()));
+            fs::create_dir_all(&path).expect("应能创建测试目录");
+            Self { path }
+        }
+
+        fn path(&self) -> &Path {
+            &self.path
+        }
+    }
+
+    impl Drop for TestDir {
+        fn drop(&mut self) {
+            let _ = fs::remove_dir_all(&self.path);
+        }
+    }
+
+    #[test]
+    fn access_events_do_not_trigger_project_scans() {
+        let access = Event::new(EventKind::Access(AccessKind::Read));
+        let create = Event::new(EventKind::Create(CreateKind::Folder));
+
+        assert!(!should_rescan(&Ok(access)));
+        assert!(should_rescan(&Ok(create)));
+    }
+
+    #[tokio::test]
+    async fn broadcasts_when_a_project_is_added() {
+        let root = TestDir::new();
+        let (updates, _) = broadcast::channel(8);
+        let mut receiver = updates.subscribe();
+
+        start(root.path().to_path_buf(), updates).expect("应能启动文件监听");
+
+        let project = root.path().join("new-project");
+        fs::create_dir_all(&project).expect("应能创建项目目录");
+        fs::write(project.join("index.html"), "<!doctype html>").expect("应能创建入口文件");
+
+        let projects = tokio::time::timeout(Duration::from_secs(5), receiver.recv())
+            .await
+            .expect("应在超时前收到项目更新")
+            .expect("项目更新通道不应关闭");
+
+        assert_eq!(projects.len(), 1);
+        assert_eq!(projects[0].name, "new-project");
+        assert_eq!(projects[0].route_path, "/new-project/");
+    }
+}