refactor: move all styles to public/assets/css

- Remove duplicate CSS files from src/assets
- Keep all stylesheets in public/assets/css for static serving
- Update style.css imports to reference public assets
- Cleaner separation: public for styles, src for Vue components

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

public/assets/css/editor-ui.css

@@ -0,0 +1 @@
+

public/assets/css/print-styles.css

@@ -0,0 +1,17 @@
+/* PagedJS print styles */
+@page {
+  size: A4;
+  margin: 20mm 15mm 26mm 15mm;
+}
+h2 {
+  break-before: page;
+}
+
+@page {
+  @bottom-center {
+    content: string(title);
+  }
+}
+.chapter > h2 {
+  string-set: title content(text);
+}