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。

stash-web/src/api.ts

@@ -0,0 +1,69 @@
+export type Project = {
+  name: string
+  route_path: string
+}
+
+type ProjectsPayload = {
+  projects?: Project[]
+}
+
+const PROJECTS_ENDPOINT = '/api/projects'
+const EVENTS_ENDPOINT = '/api/projects/events'
+
+/** 读取服务端扫描出的项目列表。 */
+export async function fetchProjects(signal?: AbortSignal): Promise<Project[]> {
+  const response = await fetch(PROJECTS_ENDPOINT, {
+    signal,
+    headers: { Accept: 'application/json' },
+  })
+
+  if (!response.ok) {
+    throw new Error(`请求 ${PROJECTS_ENDPOINT} 失败：HTTP ${response.status}`)
+  }
+
+  const payload = (await response.json()) as ProjectsPayload
+  return Array.isArray(payload.projects) ? payload.projects : []
+}
+
+export type ProjectEventsHandlers = {
+  onProjects: (projects: Project[]) => void
+  /** SSE 连接建立 / 断开时回调，浏览器的 EventSource 会自行重连。 */
+  onConnectionChange?: (connected: boolean) => void
+}
+
+/**
+ * 订阅服务端的项目快照推送。
+ * 浏览器不支持 SSE 时静默降级为空清理函数，页面仍可用手动刷新。
+ */
+export function subscribeProjects(handlers: ProjectEventsHandlers): () => void {
+  if (typeof EventSource === 'undefined') {
+    return () => {}
+  }
+
+  const source = new EventSource(EVENTS_ENDPOINT)
+
+  const handleProjects = (event: Event) => {
+    try {
+      const payload = JSON.parse((event as MessageEvent<string>).data) as ProjectsPayload
+      if (Array.isArray(payload.projects)) {
+        handlers.onProjects(payload.projects)
+      }
+    } catch {
+      // 单条事件格式异常时保留旧数据，等待下一次推送
+    }
+  }
+
+  const handleOpen = () => handlers.onConnectionChange?.(true)
+  const handleError = () => handlers.onConnectionChange?.(false)
+
+  source.addEventListener('projects', handleProjects)
+  source.addEventListener('open', handleOpen)
+  source.addEventListener('error', handleError)
+
+  return () => {
+    source.removeEventListener('projects', handleProjects)
+    source.removeEventListener('open', handleOpen)
+    source.removeEventListener('error', handleError)
+    source.close()
+  }
+}