chore: 初始化 Windows-Gotify-Client-Rust 项目骨架

使用 Rust + Slint 重建一个轻量、现代、Windows 原生体验良好的 Gotify
桌面客户端。本次只搭目录骨架与占位文件，未进入 Phase 1（Bootstrap）。

本次提交内容
------------
- 保留 AGENTS.md（1363 行定制 Agent 实施计划，含 8 阶段路线图）
- 新建 Cargo.toml（[package] 元数据 + AGENTS.md §44 依赖模板 + §42
  release profile；无 [[bin]]，等 Phase 1 才加 src/main.rs）
- 新建 README.md（项目导览，引用 AGENTS.md）
- 新建 .gitignore（Rust / Slint / Windows / IDE / 密钥）
- 新建 LICENSE（MIT 占位）
- 按 AGENTS.md §4 建好全部 10 个目录，每个空目录放 .gitkeep：
    assets/        assets/fonts/
    ui/            scripts/
    src/           src/gotify/
    src/storage/   src/windows/
    src/services/  tests/

未提交（Phase 1 起才落地）
------------------------
- src/main.rs 及所有 .rs 业务代码
- ui/*.slint 视图
- scripts/build-release.ps1 等构建脚本
- Cargo.lock（当前 Cargo.toml 是占位、无可编译代码）

技术栈约束（来自 AGENTS.md §1 / §2）
------------------------------------
- Rust stable + Slint 1.17.x + Windows 10/11
- 显式禁用：Tauri / Wails / Electron / WebView2 / WPF / WinUI 3 / Node 运行时
- 单一主程序，无浏览器运行时依赖；UI 由 Slint 原生渲染

仓库
----
远程：https://gitea.kennethcheng.cc/KennethCheng/Windows-Gotify-Client-Rust

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 KennethCheng
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.