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/conf.py

@@ -15,19 +15,73 @@ project = 'revpimodio2'
 copyright = '2023, Sven Sager'
 author = 'Sven Sager'
 version = __version__
+release = __version__
 
 # -- General configuration ---------------------------------------------------
 
 extensions = [
     'sphinx.ext.autodoc',
+    'sphinx.ext.napoleon',
+    'sphinx.ext.viewcode',
+    'sphinx.ext.intersphinx',
+    'sphinx.ext.autosummary',
     'sphinx.ext.todo',
-    'sphinx.ext.viewcode'
 ]
 
+# Autodoc configuration
+autodoc_default_options = {
+    'members': True,
+    'member-order': 'bysource',
+    'special-members': '__init__',
+    'undoc-members': True,
+    'exclude-members': '__weakref__'
+}
+
+# Napoleon settings (for NumPy and Google style docstrings)
+napoleon_google_docstring = True
+napoleon_numpy_docstring = True
+napoleon_include_init_with_doc = True
+napoleon_include_private_with_doc = False
+napoleon_include_special_with_doc = True
+napoleon_use_admonition_for_examples = True
+napoleon_use_admonition_for_notes = True
+napoleon_use_admonition_for_references = True
+napoleon_use_ivar = False
+napoleon_use_param = True
+napoleon_use_rtype = True
+napoleon_preprocess_types = True
+napoleon_type_aliases = None
+napoleon_attr_annotations = True
+
+# Autosummary settings
+autosummary_generate = True
+
+# Intersphinx configuration
+intersphinx_mapping = {
+    'python': ('https://docs.python.org/3', None),
+}
+
+# Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
+
+# List of patterns, relative to source directory, that match files and
+# directories to ignore when looking for source files.
 exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
 
 # -- Options for HTML output -------------------------------------------------
 
-html_theme = 'alabaster'
+html_theme = 'sphinx_rtd_theme'
 html_static_path = ['_static']
+
+# Theme options
+html_theme_options = {
+    'navigation_depth': 4,
+    'collapse_navigation': False,
+    'sticky_navigation': True,
+    'includehidden': True,
+    'titles_only': False
+}
+
+# -- Options for todo extension ----------------------------------------------
+
+todo_include_todos = True