Enhance documentation and configuration for static site generator

- Update README for clarity and quick start instructions
- Refine default config.toml with hostname and base path
- Adjust index.md files for consistent heading levels
- Simplify CSS for code block styling and remove unnecessary theme switching
- Refactor SiteConfig to derive full base URL from hostname and base path
- Update MarkdownRenderer to remove light theme handling

docs/css/main.css

@@ -304,7 +304,7 @@ a:hover {
 }
 
 .content article pre {
-  background: var(--bg-code) !important;
+  background: var(--bg-code);
   color: var(--text-code);
   padding: 16px;
   border-radius: 4px;
@@ -426,13 +426,6 @@ a:hover {
   --nav-section-active: #333;
 }
 
-/* Code block theme switching */
-.code-light { display: none; }
-.code-dark { display: block; }
-
-[data-theme="light"] .code-light { display: block; }
-[data-theme="light"] .code-dark { display: none; }
-
 /* Theme toggle */
 .theme-toggle {
   display: flex;