feat: Implement initial tuner application with core logic, audio processing, and presentation components.

README.md

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+# AeroTuner
+
+An instrument tuner featuring a nostalgic **Frutiger Aero** aesthetic, built with modern web technologies and Clean Architecture.
+
+![Status](https://img.shields.io/badge/Status-Production_Ready-success)
+![PWA](https://img.shields.io/badge/PWA-Installable-purple)
+![Tests](https://img.shields.io/badge/Tests-Passing-green)
+![Design](https://img.shields.io/badge/Design-Frutiger%20Aero-aqua)
+
+## Features
+
+### Precision Tuning
+- **FFT-based Pitch Detection**: High-precision frequency analysis using the Web Audio API.
+- **Harmonic Product Spectrum (HPS)**: Robust fundamental frequency detection, even for bass instruments.
+- **Accurate to ±1 cent**: Professional-grade tuning accuracy (don't quote me on that).
+- **Multi-Instrument Support**: Guitar, Ukulele, Bass, and Piano.
+- **Alternate Tunings**: Drop D, Open G, DADGAD, and more (Pro Mode).
+
+### Frutiger Aero UI
+- **Glossy Aesthetics**: Glassmorphism, vibrant gradients, and detailed reflections.
+- **Interactive Gauge**: Smooth, physics-based needle animation.
+- **Basic vs. Pro Modes**:
+    - **Basic**: Clean interface for quick tuning.
+    - **Pro**: Advanced tools including Waveform Display and String Guide.
+- **Real-time Waveform**: Visualizes the audio signal in real-time.
+- **String Guide**: Visual indicator of the target string.
+
+### Progressive Web App (PWA)
+- **Installable**: Add to home screen on iOS, Android, and Desktop.
+- **Offline Capable**: Works without an internet connection.
+- **App-like Experience**: Fullscreen mode with custom icons.
+
+## Technology Stack
+
+- **Core**: [React 19](https://react.dev/), [TypeScript](https://www.typescriptlang.org/)
+- **Build**: [Vite](https://vitejs.dev/), [Bun](https://bun.sh/)
+- **Styling**: [Tailwind CSS](https://tailwindcss.com/) (with custom Frutiger Aero configuration)
+- **Audio**: Web Audio API (`AnalyserNode`, `AudioContext`)
+- **State**: React Hooks + LocalStorage persistence
+- **Testing**: [Bun Test](https://bun.sh/docs/cli/test)
+
+## Architecture
+
+This project strictly follows **Clean Architecture** principles to ensure maintainability and testability:
+
+- **Domain Layer** (`src/domain`): Pure business logic (Note conversion, Tuning calculations, Harmonic analysis). Zero dependencies.
+- **Infrastructure Layer** (`src/infrastructure`): Implementation details (Web Audio API, FFT algorithms).
+- **Presentation Layer** (`src/presentation`): UI components and React hooks.
+
+## Quick Start
+
+```bash
+# Install dependencies
+bun install
+
+# Start development server
+bun dev
+
+# Run tests
+bun test
+
+# Build for production
+bun run build
+```
+
+## Testing
+
+The project includes a comprehensive suite of unit tests for the Domain layer.
+
+```bash
+bun test
+```
+
+Tests cover:
+- Frequency ↔ Note conversion
+- Cents calculation & Tuning status
+- Harmonic analysis & Fundamental frequency detection
+
+## Usage
+
+1.  **Grant Permission**: Allow microphone access when prompted.
+2.  **Select Instrument**: Choose Guitar, Bass, Ukulele, or Piano.
+3.  **Choose Mode**: Toggle between **Basic** (simple) and **Pro** (advanced) views.
+4.  **Tune**: Play a string. The gauge shows if you are sharp (right) or flat (left).
+    - **Green**: In tune!
+    - **Blue/Red**: Adjust your tuning pegs.
+
+## License
+
+MIT