docs: Switch to shibuya theme with compatibility fixes

Configure documentation to use the shibuya theme (python3-shibuya-sphinx-theme) with proper compatibility fixes.

Changes:

- Switched html_theme from alabaster to shibuya

- Added monkey patch to fix incompatibility between shibuya's hardcoded pygments styles (github-light-default, github-dark-default) and available pygments version

- Override ShibuyaPygmentsBridge class attributes to use available styles:

  * light_style_name: default

  * dark_style_name: github-dark

- Configured shibuya theme options with GitHub URL and navigation links

- Enabled dark_code option for better code syntax highlighting

Build Status:

- Documentation builds successfully ✅

- 226 warnings (existing legacy content formatting)

- Shibuya theme renders correctly with proper light/dark mode support

This resolves the pygments.util.ClassNotFound error for 'github-dark-default' style and enables the modern shibuya theme for MultiFlexi documentation.

Co-Authored-By: Warp <agent@warp.dev>

Author: Vitexus

docs/source/conf.py

@@ -1,5 +1,11 @@
 # Configuration file for the Sphinx documentation builder.
 
+# Monkey patch shibuya to use available pygments styles
+import shibuya._pygments
+# Override shibuya's default styles with available ones
+shibuya._pygments.ShibuyaPygmentsBridge.light_style_name = "default"
+shibuya._pygments.ShibuyaPygmentsBridge.dark_style_name = "github-dark"
+
 # -- Project information
 
 project = 'MultiFlexi'
@@ -47,16 +53,21 @@
 
 # -- Options for HTML output
 
-html_theme = "alabaster"
+html_theme = "shibuya"
 
-# Pygments styling
+# Pygments styling - use valid styles for light and dark modes
 pygments_style = "default"
+pygments_dark_style = "github-dark"  # Use available github-dark instead of github-dark-default
 
 html_theme_options = {
-    'github_user': 'VitexSoftware',
-    'github_repo': 'MultiFlexi',
-    'github_button': True,
-    'github_type': 'star',
+    "github_url": "https://github.com/VitexSoftware/MultiFlexi",
+    "dark_code": True,
+    "nav_links": [
+        {
+            "title": "GitHub",
+            "url": "https://github.com/VitexSoftware/MultiFlexi",
+        },
+    ],
 }
 
 # Show source links