docs: migrate content files to TOML frontmatter

Migrate all 17 docs/content/ files from --- YAML to +++ TOML
frontmatter delimiters and key = value syntax.

Update 8 embedded frontmatter examples in 7 documentation pages
to match (configuration, content-organization, getting-started,
security, sections, sitemap, feeds, templates).

Update configuration.md frontmatter reference table: add draft
and aliases fields, correct date type from string to date.

docs/content/architecture.md

@@ -1,9 +1,9 @@
----
-title: "Architecture"
-description: "How sukr transforms markdown into zero-JS static sites"
-weight: 5
-toc: true
----
++++
+title = "Architecture"
+description = "How sukr transforms markdown into zero-JS static sites"
+weight = 5
+toc = true
++++
 
 sukr is a 13-module static site compiler. Every feature that would typically require client-side JavaScript is moved to build-time.