feat: add minimal base CSS with dark mode support

- static/style.css: CSS variable-based theming with:
  - Typography (system fonts, monospace for code)
  - Layout (centered content, nav/main/footer structure)
  - Dark mode via prefers-color-scheme
  - Component styles (posts, cards, tags, hero)

- src/main.rs: Add copy_static_assets() to copy static/
  directory to public/ during build

Phase 1 complete. Ready for syntax highlighting.

src/content.rs

@@ -1,7 +1,7 @@
 //! Content discovery and frontmatter parsing.
 
 use crate::error::{Error, Result};
-use gray_matter::{Matter, engine::YAML};
+use gray_matter::{engine::YAML, Matter};
 use std::fs;
 use std::path::{Path, PathBuf};
 

src/main.rs

@@ -22,11 +22,15 @@ fn main() {
 fn run() -> Result<()> {
     let content_dir = Path::new("content");
     let output_dir = Path::new("public");
+    let static_dir = Path::new("static");
 
     if !content_dir.exists() {
         return Err(Error::ContentDirNotFound(content_dir.to_path_buf()));
     }
 
+    // 0. Copy static assets
+    copy_static_assets(static_dir, output_dir)?;
+
     // 1. Process blog posts
     let mut posts = process_blog_posts(content_dir, output_dir)?;
 
@@ -208,3 +212,41 @@ fn write_output(
     eprintln!("  → {}", out_path.display());
     Ok(())
 }
+
+/// Copy static assets (CSS, etc.) to output directory
+fn copy_static_assets(static_dir: &Path, output_dir: &Path) -> Result<()> {
+    if !static_dir.exists() {
+        return Ok(()); // No static dir is fine
+    }
+
+    fs::create_dir_all(output_dir).map_err(|e| Error::CreateDir {
+        path: output_dir.to_path_buf(),
+        source: e,
+    })?;
+
+    for entry in walkdir::WalkDir::new(static_dir)
+        .into_iter()
+        .filter_map(|e| e.ok())
+        .filter(|e| e.file_type().is_file())
+    {
+        let src = entry.path();
+        let relative = src.strip_prefix(static_dir).unwrap();
+        let dest = output_dir.join(relative);
+
+        if let Some(parent) = dest.parent() {
+            fs::create_dir_all(parent).map_err(|e| Error::CreateDir {
+                path: parent.to_path_buf(),
+                source: e,
+            })?;
+        }
+
+        fs::copy(src, &dest).map_err(|e| Error::WriteFile {
+            path: dest.clone(),
+            source: e,
+        })?;
+
+        eprintln!("copying: {} → {}", src.display(), dest.display());
+    }
+
+    Ok(())
+}

src/templates.rs

@@ -1,7 +1,7 @@
 //! HTML templates using maud.
 
 use crate::content::{Content, Frontmatter};
-use maud::{DOCTYPE, Markup, PreEscaped, html};
+use maud::{html, Markup, PreEscaped, DOCTYPE};
 
 /// Render a blog post with the base layout.
 pub fn render_post(frontmatter: &Frontmatter, content_html: &str) -> Markup {