Adds comprehensive documentation.

docs/installation.md

@@ -0,0 +1,77 @@
+# Installation Guide
+
+**Nextcloud Upload Tool (`nut`)** is available as a standalone command-line tool and a desktop GUI application across macOS, Windows, and Linux.
+
+---
+
+## 1. Pre-built Binaries & Installers
+
+Download pre-built releases for your operating system from the [Releases](https://github.com/majinnaibu/nextcloud-upload-tool/releases) page.
+
+### macOS (Apple Silicon & Intel)
+- **GUI Desktop App**: Download the `.dmg` installer, open it, and drag `Nextcloud Upload Tool.app` into `/Applications`.
+- **CLI Binary**:
+  ```bash
+  # Apple Silicon (M1/M2/M3/M4)
+  curl -fsSL https://github.com/majinnaibu/nextcloud-upload-tool/releases/latest/download/nut-aarch64-apple-darwin.tar.gz | tar -xz
+  sudo mv nut /usr/local/bin/
+
+  # Intel x86_64
+  curl -fsSL https://github.com/majinnaibu/nextcloud-upload-tool/releases/latest/download/nut-x86_64-apple-darwin.tar.gz | tar -xz
+  sudo mv nut /usr/local/bin/
+  ```
+
+### Linux (Debian, Ubuntu, Fedora, Arch, Generic)
+- **Debian / Ubuntu (`.deb`)**:
+  ```bash
+  sudo dpkg -i nextcloud-upload-tool_0.1.0_amd64.deb
+  sudo apt-get install -f
+  ```
+- **Fedora / RHEL (`.rpm`)**:
+  ```bash
+  sudo rpm -i nextcloud-upload-tool-0.1.0-1.x86_64.rpm
+  ```
+- **Universal AppImage**:
+  ```bash
+  chmod +x Nextcloud_Upload_Tool_0.1.0_amd64.AppImage
+  ./Nextcloud_Upload_Tool_0.1.0_amd64.AppImage
+  ```
+- **Static CLI Binary (musl libc - zero external dependencies)**:
+  ```bash
+  curl -fsSL https://github.com/majinnaibu/nextcloud-upload-tool/releases/latest/download/nut-x86_64-unknown-linux-musl.tar.gz | tar -xz
+  sudo mv nut /usr/local/bin/
+  ```
+
+### Windows
+- **GUI Installer (`.msi` / NSIS `.exe`)**: Download and run `Nextcloud-Upload-Tool-Setup.exe` or `Nextcloud-Upload-Tool.msi`. Follow the installer wizard.
+- **Standalone CLI**: Download `nut-x86_64-pc-windows-msvc.zip`, extract `nut.exe`, and add it to your system `%PATH%`.
+
+---
+
+## 2. Building from Source
+
+### Prerequisites
+- **Rust toolchain** (1.75+): Install via `curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh`
+- **Node.js** (v20+) and **npm** (for GUI frontend build)
+- **Platform Development Libraries**:
+  - **Linux**: `sudo apt-get install libwebkit2gtk-4.1-dev libappindicator3-dev librsvg2-dev libssl-dev patchelf`
+  - **macOS**: Xcode Command Line Tools (`xcode-select --install`)
+  - **Windows**: Visual Studio C++ Build Tools
+
+### Build the CLI (`nut`)
+```bash
+git clone https://github.com/majinnaibu/nextcloud-upload-tool.git
+cd nextcloud-upload-tool
+
+cargo build --release -p nut
+# The binary is placed at target/release/nut
+```
+
+### Build the Desktop GUI
+```bash
+cd gui
+npm install
+npm run build
+npm run tauri build
+# The packaged bundle is located in gui/src-tauri/target/release/bundle/
+```