feat: Additive merge of webui branch with PyQt GUI support

- Add abogen/pyqt/ package with full PyQt6 desktop GUI
- Restore PyQt GUI files (gui.py, book_handler.py, queue_manager_gui.py, voice_formula_gui.py, conversion.py)
- Add new shared modules from webui: book_parser.py, subtitle_utils.py, spacy_utils.py
- Add Linux libraries (libxcb-cursor) for Qt platform plugin support
- Add new epub parsing tests from webui branch
- Update pyproject.toml with dual entry points:
  - abogen: PyQt6 desktop GUI
  - abogen-web: Flask Web UI
- Add PyQt6 to dependencies
- Re-export PyQt classes from root modules for backwards compatibility
- Merge CHANGELOG.md entries (1.2.0-1.2.5 from webui)
- Update README.md with dual interface documentation

Implements #26 - shared core with separate UI folders

README.md

@@ -9,6 +9,17 @@ Abogen is a web-first text-to-speech workstation. Drop in an EPUB, PDF, Markdown
 - LLM-assisted text normalization with live previews and configurable prompts
 - Runs well in Docker, ships a REST-style JSON API, and works across macOS, Linux, and Windows
 
+## Interfaces
+
+Abogen offers **two interfaces** to suit different workflows:
+
+| Command | Interface | Best for |
+|---------|-----------|----------|
+| `abogen` | PyQt6 Desktop GUI | Local desktop use on Windows/macOS/Linux |
+| `abogen-web` | Flask Web UI | Docker, headless servers, remote access |
+
+Both interfaces share the same core processing engine and produce identical output.
+
 ## Quick start
 Abogen supports Python 3.10–3.12.
 
@@ -19,11 +30,16 @@ source .venv/bin/activate  # On Windows use: .venv\Scripts\activate
 pip install abogen
 ```
 
-### Launch the web app
+### Launch the desktop app (PyQt6)
 ```bash
 abogen
 ```
 
+### Launch the web app (Flask)
+```bash
+abogen-web
+```
+
 Then open http://localhost:8808 and drag in your documents. Jobs run in the background worker and the browser updates automatically.
 
 > **Tip:** Keep the terminal open while the server is running. Use `Ctrl+C` to stop it.