feat: add comprehensive documentation website with mdBook

Add professional documentation site covering all aspects of Whisper Hotkey.

## Changes

- Add mdBook configuration and structure
- Create GitHub Actions workflow for automatic deployment to GitHub Pages
- Add documentation badge to README
- Add mdbook to mise.toml for tool management

## Documentation Sections

**Getting Started:**
- Installation (Homebrew, DMG, build from source)
- Quick Start guide with test procedures
- macOS Permissions setup and troubleshooting

**Usage:**
- Basic usage and workflow
- Hotkey configuration
- Multi-profile support with examples
- Alias matching for common phrases

**Configuration:**
- Complete configuration reference (all options)
- Audio settings (buffer size, sample rate)
- Model selection comparison (tiny → large)
- Performance tuning strategies

**Development:**
- Project structure and architecture
- Building from source (mise, cargo)
- Testing strategy (unit, integration, coverage)
- Contributing guidelines

**Troubleshooting:**
- Common issues (installation, audio, hotkeys)
- Permission problems (detailed macOS TCC guide)
- Performance issues (profiling, optimization)

## Implementation Details

- mdBook 0.4.43 for static site generation
- GitHub Actions for automatic deployment on push to main
- Comprehensive cross-referencing between sections
- Code examples and command snippets throughout
- Structured navigation with logical grouping

## Next Steps

After merging:
1. Enable GitHub Pages in repo settings (Source: GitHub Actions)
2. Documentation will be available at https://automaat.github.io/whisper-hotkey/
3. Badge in README links to live docs

## Supporting documentation

Implements issue #49: #49

Signed-off-by: Marcin Skalski <skalskimarcin33@gmail.com>

Author: Automaat

.github/workflows/docs.yml

@@ -0,0 +1,53 @@
+name: Deploy Documentation
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+      - '.github/workflows/docs.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup mdBook
+        uses: peaceiris/actions-mdbook@v2
+        with:
+          mdbook-version: '0.4.43'
+
+      - name: Build documentation
+        run: cd docs && mdbook build
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v4
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./docs/book
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.mise.toml

@@ -2,6 +2,7 @@
 rust = "1.91"  # edition2024 support for coreaudio-sys
 shellcheck = "0.11.0"
 actionlint = "1.7.9"
+mdbook = "0.4.43"
 
 [tasks.check]
 description = "Run all linters"

README.md

@@ -1,5 +1,7 @@
 # whisper-hotkey
 
+[![Documentation](https://img.shields.io/badge/docs-latest-blue.svg)](https://automaat.github.io/whisper-hotkey/)
+
 ![Whisper Hotkey logo](resources/logo.png)
 
 macOS background app for system-wide voice-to-text via hotkey using local Whisper.

docs/.gitignore

@@ -0,0 +1 @@
+book/

docs/book.toml

@@ -0,0 +1,15 @@
+[book]
+authors = ["Marcin Skalski"]
+language = "en"
+multilingual = false
+src = "src"
+title = "Whisper Hotkey Documentation"
+description = "macOS background app for system-wide voice-to-text via hotkey using local Whisper"
+
+[build]
+build-dir = "book"
+
+[output.html]
+git-repository-url = "https://github.com/Automaat/whisper-hotkey"
+edit-url-template = "https://github.com/Automaat/whisper-hotkey/edit/main/docs/{path}"
+site-url = "/whisper-hotkey/"

docs/src/SUMMARY.md

@@ -0,0 +1,36 @@
+# Summary
+
+[Introduction](./introduction.md)
+
+# Getting Started
+
+- [Installation](./getting-started/installation.md)
+- [Quick Start](./getting-started/quick-start.md)
+- [macOS Permissions](./getting-started/permissions.md)
+
+# Usage
+
+- [Basic Usage](./usage/basic.md)
+- [Hotkeys](./usage/hotkeys.md)
+- [Multi-Profile Support](./usage/profiles.md)
+- [Alias Matching](./usage/alias-matching.md)
+
+# Configuration
+
+- [Configuration Reference](./configuration/reference.md)
+- [Audio Settings](./configuration/audio.md)
+- [Model Selection](./configuration/models.md)
+- [Performance Tuning](./configuration/performance.md)
+
+# Development
+
+- [Project Structure](./development/structure.md)
+- [Building from Source](./development/building.md)
+- [Testing](./development/testing.md)
+- [Contributing](./development/contributing.md)
+
+# Troubleshooting
+
+- [Common Issues](./troubleshooting/common-issues.md)
+- [Permissions Problems](./troubleshooting/permissions.md)
+- [Performance Issues](./troubleshooting/performance.md)

docs/src/chapter_1.md

@@ -0,0 +1 @@
+# Chapter 1