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。

Cargo.toml

@@ -1,18 +1,30 @@
-[workspace]
-resolver = "2"
-members = [
-    "stash-core",
-    "stash-cli",
-]
-
-[workspace.package]
+[package]
+name = "stash"
 version = "0.1.0"
+description = ""
+authors = [""]
 edition = "2024"
-license = "MIT OR Apache-2.0"
 
-[workspace.dependencies]
+[dependencies]
 tokio = { version = "1.38", features = ["full"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
-thiserror = "1.0"
-anyhow = "1.0"
+thiserror = "2.0.21"
+anyhow = "1.0"
+clap = { version = "4.6.7", features = ["derive"] }
+colored = "3.1.1"
+
+# Web 核心与静态托管
+axum = "0.8.9"
+tower-http = { version = "0.7.1", features = ["fs", "cors", "trace"] }
+tower = { version = "0.4", features = ["util"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+mime_guess = "2.0"
+include_dir = "0.7"
+async-stream = "0.3"
+notify = "8"
+
+[build-dependencies]
+# build.rs 用它递归复制前端产物到 $OUT_DIR/web
+walkdir = "2.4"