Phase 1: Fix markdown rendering

- Add rawHTML helper function using template.HTML()
- Update docs template to use { template.HTML(doc.Content) }
- Docs now render HTML headings and content properly
- Markdown is converted to HTML by goldmark (with Unsafe()) and output directly

templates/types.go

@@ -160,3 +160,6 @@ type BreadcrumbItem struct {
 	Title string
 	URL   string
 }
+
+// UnsafeHTML is used for rendering raw HTML (like rendered markdown)
+type UnsafeHTML string