chore: import upstream snapshot with attribution

packaging/linux/README-LINUX.txt

@@ -0,0 +1,77 @@
+StemDeck Linux Portable Alpha
+=============================
+
+This comes in two variants. Pick one:
+
+- StemDeck-Linux-x64.tar.gz         CPU-only (smaller; runs anywhere)
+- StemDeck-Linux-x64.NVIDIA.tar.gz  NVIDIA/CUDA (larger; much faster on an
+                                    NVIDIA GPU, falls back to CPU if no GPU)
+
+Run
+---
+
+1. Extract the tarball, e.g.:
+     tar -xzf StemDeck-Linux-x64.tar.gz
+2. Install the runtime prerequisites (see below).
+3. Run the launcher:
+     cd StemDeck-Linux-x64        # or StemDeck-Linux-x64.NVIDIA
+     ./StemDeck
+4. Let first-run setup prepare local runtime assets.
+
+Prerequisites
+-------------
+
+This portable package bundles its own Python runtime (torch + demucs), and
+StemDeck downloads FFmpeg automatically on first launch (or uses a system
+`ffmpeg` if one is already on your PATH). The only system libraries you need
+are your distro's WebKitGTK + GTK, which the desktop shell links against.
+
+  Debian / Ubuntu:
+    sudo apt update
+    sudo apt install libwebkit2gtk-4.1-0 libgtk-3-0
+
+  Fedora:
+    sudo dnf install webkit2gtk4.1 gtk3
+
+  Arch:
+    sudo pacman -S webkit2gtk-4.1 gtk3
+
+NVIDIA variant
+--------------
+
+To use the GPU you need a working NVIDIA driver on the host such that
+`nvidia-smi` runs and reports your GPU.
+
+  Check your driver:
+    nvidia-smi
+
+On first launch, the NVIDIA build detects your GPU and downloads the matching
+CUDA-enabled PyTorch (a few GB) into your data directory — so the first run
+needs an internet connection and some disk space. You do NOT need a separate
+CUDA toolkit install, only the driver.
+
+If no usable GPU is detected, the NVIDIA build still runs and falls back to CPU.
+If you do not have an NVIDIA GPU, use the CPU-only tarball instead — it skips
+the CUDA download entirely.
+
+Notes
+-----
+
+- This is a portable folder, not a system package. No .desktop entry, service,
+  or package-manager integration is created.
+- User data lives under $XDG_DATA_HOME/stemdeck (or ~/.local/share/stemdeck).
+- Your stem library is written to ~/Documents/StemDeck/.
+- Demucs model weights download from the backend on first use into the data
+  directory under models/.
+
+Troubleshooting
+---------------
+
+- "./StemDeck: error while loading shared libraries" — install the WebKitGTK
+  and GTK packages listed above.
+- A job failing immediately with an FFmpeg error — first-run setup downloads
+  FFmpeg automatically; check internet access and retry, or install a system
+  `ffmpeg` so `ffmpeg -version` works in your shell.
+- If setup fails, check internet access and retry.
+- Inspect logs under the data directory's logs/ folder.
+- Deleting the data directory forces first-run setup to recreate runtime state.

packaging/linux/THIRD_PARTY_NOTICES.txt

@@ -0,0 +1,78 @@
+THIRD-PARTY NOTICES
+===================
+
+StemDeck includes third-party open-source software. Each component is
+copyrighted by its respective authors and distributed under its own license.
+
+This starter notice is not a substitute for the full license inventory that
+must be generated from the final packaged Python runtime before a public
+release.
+
+Bundled Components
+------------------
+
+Python
+License: Python Software Foundation License
+Website: https://www.python.org/
+
+Tauri
+License: MIT or Apache-2.0, depending on component
+Website: https://tauri.app/
+
+FastAPI
+License: MIT
+Website: https://fastapi.tiangolo.com/
+
+Uvicorn
+License: BSD
+Website: https://www.uvicorn.org/
+
+yt-dlp
+License: Unlicense
+Website: https://github.com/yt-dlp/yt-dlp
+
+Demucs
+License: MIT
+Website: https://github.com/facebookresearch/demucs
+
+PyTorch / Torch
+License: BSD-style
+Website: https://pytorch.org/
+
+torchaudio
+License: BSD-style
+Website: https://pytorch.org/audio/
+
+librosa
+License: ISC
+Website: https://librosa.org/
+
+pyloudnorm
+License: MIT
+Website: https://github.com/csteinmetz1/pyloudnorm
+
+soundfile
+License: BSD
+Website: https://github.com/bastibe/python-soundfile
+
+System Requirements (Not Bundled)
+---------------------------------
+
+FFmpeg is not bundled in the Linux package. On first launch StemDeck downloads a
+static FFmpeg build into your user data directory (or uses a system `ffmpeg`
+already on your PATH). The download is fetched directly from the upstream
+provider, not redistributed by StemDeck. FFmpeg may be distributed under LGPL or
+GPL terms depending on how the build was compiled.
+
+WebKitGTK and GTK shared libraries are provided by your Linux distribution and
+are not bundled. They are distributed under LGPL terms.
+
+Demucs model weights are not bundled. They are downloaded during first use.
+StemDeck should display the model source and license/usage terms before or
+during download.
+
+Disclaimer
+----------
+
+This notice file is not legal advice. Before public release, verify the exact
+licenses of every bundled package and generated binary artifact.