IMPROVE: thêm tập tin LICENSE của dự án

LICENSE

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+MIT License
+
+Copyright (c) 2026 SonicForge Studio contributors
+
+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.
+
+---
+
+## Third-party components
+
+Code viết riêng của dự án (app/static/js/services/*, components/*, app.jsx)
+thuộc license MIT trên.
+
+Các thành phần bên thứ ba giữ license gốc:
+
+- **React / react-dom** — MIT
+- **Babel** (@babel/cli, core, preset-react) — MIT
+- **jsdom** — MIT
+- **Tailwind CSS** (app/static/css/tailwind.min.css) — MIT
+- **Lucide icons** — ISC
+- **FluidSynth 2.3.0** (app/static/js/vendor/libfluidsynth-2.3.0-sf3.js/.wasm) —
+  GNU LGPL v2.1+ — xem https://www.gnu.org/licenses/lgpl-2.1.html
+
+Chi tiết + attribution từng thành phần: xem THIRD_PARTY_LICENSES.md.