docs: restructure documentation into organized files

Split the 630-line README.md into focused, well-organized documentation:

- README.md: Concise overview with quick start and links
- docs/INSTALLATION.md: Installation instructions and setup
- docs/CONFIGURATION.md: Configuration options and custom categories
- docs/USAGE.md: Command-line options and usage examples
- docs/HOW_IT_WORKS.md: Architecture and internal processes
- docs/TROUBLESHOOTING.md: Common issues and solutions
- docs/DEVELOPMENT.md: Project structure and development guide
- docs/CONTRIBUTING.md: Contribution guidelines and standards

Benefits:
- Main README is now clean and welcoming (~150 lines vs 630)
- Each doc has a clear, focused purpose
- Better navigation with cross-linking between docs
- Follows GitHub best practices with docs/ directory
- Easier to maintain and update specific sections

docs/INSTALLATION.md

@@ -0,0 +1,121 @@
+# Installation Guide
+
+This guide covers different ways to install and set up NoEntropy on your system.
+
+## Prerequisites
+
+Before installing NoEntropy, ensure you have:
+
+- **Rust 2024 Edition** or later (if building from source)
+- **Google Gemini API Key** - Get one at [https://ai.google.dev/](https://ai.google.dev/)
+- A folder full of unorganized files to clean up!
+
+## Option 1: Download Pre-built Binary
+
+The easiest way to get started is to download a pre-built binary for your operating system.
+
+1. **Download Binary**
+   
+   Visit the releases page and download the binary for your operating system (Windows, Linux, or macOS):
+   ```bash
+   https://github.com/glitchySid/noentropy/releases
+   ```
+
+2. **Give Permission (Linux/macOS only)**
+   
+   Make the binary executable:
+   ```bash
+   chmod +x noentropy
+   ```
+
+3. **Run NoEntropy**
+   
+   ```bash
+   ./noentropy
+   ```
+
+## Option 2: Build from Source
+
+If you prefer to build from source or want the latest development version:
+
+1. **Clone the Repository**
+   
+   ```bash
+   git clone https://github.com/glitchySid/noentropy.git
+   cd noentropy
+   ```
+
+2. **Build the Application**
+   
+   ```bash
+   cargo build --release
+   ```
+
+3. **Run the Application**
+   
+   ```bash
+   ./target/release/noentropy
+   ```
+
+## First-Run Setup
+
+On first run, NoEntropy will guide you through an interactive setup process:
+
+### Interactive Setup
+
+NoEntropy provides an interactive setup if configuration is missing:
+
+- **Missing API key?** → You'll be prompted to enter it
+- **Missing download folder?** → You'll be prompted to specify it (with default suggestion)
+- **Both missing?** → You'll be guided through complete setup
+
+Configuration is automatically saved to `~/.config/noentropy/config.toml` after interactive setup.
+
+### Manual Configuration
+
+Alternatively, you can manually create the configuration file:
+
+```bash
+cp config.example.toml ~/.config/noentropy/config.toml
+nano ~/.config/noentropy/config.toml
+```
+
+See the [Configuration Guide](CONFIGURATION.md) for detailed configuration options.
+
+## Getting Your Gemini API Key
+
+1. Visit [Google AI Studio](https://ai.google.dev/)
+2. Sign in with your Google account
+3. Create a new API key
+4. Copy the key to your configuration file or enter it during interactive setup
+
+## Verification
+
+To verify your installation works correctly:
+
+1. Run NoEntropy with the `--dry-run` flag:
+   ```bash
+   ./noentropy --dry-run
+   ```
+
+2. You should see NoEntropy scan your downloads folder and display an organization plan without moving any files.
+
+## Next Steps
+
+- [Configure NoEntropy](CONFIGURATION.md) - Learn about configuration options
+- [Usage Guide](USAGE.md) - Learn how to use NoEntropy effectively
+- [How It Works](HOW_IT_WORKS.md) - Understand the organization process
+
+## Troubleshooting
+
+If you encounter issues during installation, check the [Troubleshooting Guide](TROUBLESHOOTING.md).
+
+Common installation issues:
+
+- **Rust not installed**: Install Rust from [rustup.rs](https://rustup.rs/)
+- **Build errors**: Ensure you have the latest Rust toolchain: `rustup update`
+- **Permission denied**: Make sure the binary has execute permissions (Linux/macOS)
+
+---
+
+[Back to Main README](../README.md)