docs: add comprehensive documentation structure and API reference

Created topic-based documentation:
- basics.rst: core concepts and fundamental usage
- cyclic_programming.rst: PLC-style programming with Cycletools
- event_programming.rst: event-driven patterns and callbacks
- advanced.rst: gateway IOs, replace_io_file, watchdog management
- installation.rst and quickstart.rst: getting started guides

Added complete API reference in docs/api/:
- All device classes including ModularBaseConnect_4_5 and GatewayMixin
- I/O, helper, and main class documentation

Enhanced Sphinx configuration with RTD theme and improved autodoc settings.
Removed auto-generated modules.rst and revpimodio2.rst.

docs/api/device.rst

@@ -0,0 +1,163 @@
+==============
+Device Classes
+==============
+
+Classes for managing Revolution Pi devices.
+
+.. currentmodule:: revpimodio2.device
+
+Device
+======
+
+.. autoclass:: Device
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Base class for all Revolution Pi devices.
+
+DeviceList
+==========
+
+.. autoclass:: DeviceList
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__, __getitem__, __iter__
+
+   Container for accessing devices.
+
+   **Example:**
+
+   .. code-block:: python
+
+       # Access device by name
+       dio_module = rpi.device.DIO_Module_1
+
+       # Access device by position
+       first_device = rpi.device[0]
+
+       # Iterate all devices
+       for device in rpi.device:
+           print(f"Device: {device.name}")
+
+Base
+====
+
+.. autoclass:: Base
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Base class for Revolution Pi base modules.
+
+GatewayMixin
+============
+
+.. autoclass:: GatewayMixin
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
+   Mixin class providing gateway functionality for piGate modules.
+
+ModularBaseConnect_4_5
+======================
+
+.. autoclass:: ModularBaseConnect_4_5
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Base class for Connect 4 and Connect 5 modules.
+
+Core
+====
+
+.. autoclass:: Core
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Revolution Pi Core module.
+
+Connect
+=======
+
+.. autoclass:: Connect
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Revolution Pi Connect module.
+
+Connect4
+========
+
+.. autoclass:: Connect4
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Revolution Pi Connect 4 module.
+
+Connect5
+========
+
+.. autoclass:: Connect5
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Revolution Pi Connect 5 module.
+
+DioModule
+=========
+
+.. autoclass:: DioModule
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Digital I/O module.
+
+RoModule
+========
+
+.. autoclass:: RoModule
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Relay output module.
+
+Gateway
+=======
+
+.. autoclass:: Gateway
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Gateway module (ModbusTCP, Profinet, etc.).
+
+Virtual
+=======
+
+.. autoclass:: Virtual
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :special-members: __init__
+
+   Virtual device for custom applications.