Port homepage, posts section, shortcodes; update hugo.toml menus

- content/_index.md: homepage with site description and callout examples
- content/posts/asw-vocabulary.md: ASW data-* attribute vocabulary reference
- content/posts/getting-started.md: ASW-Hugo setup guide (updated URLs)
- hugo.toml: add params, taxonomies, menus (main + docs sidebar), ToC settings
- layouts/partials/nav.html: dynamic Hugo menu rendering (was hardcoded)
- layouts/shortcodes/callout.html, wikilink.html: ported from asw-hugo theme

Closes: asw#17, asw#13, asw#11, asw#16
28 pages build clean, deploy confirmed at port 8000.

layouts/shortcodes/callout.html

@@ -0,0 +1,16 @@
+{{- /*
+  callout shortcode — wraps content in an ASW callout block.
+  
+  Usage:
+    {{< callout note >}}
+    Content here. Markdown is rendered.
+    {{< /callout >}}
+  
+  First positional param: callout type.
+  Valid types: note, warning, tip, info (maps to ASW data-callout attribute).
+  Default: note
+*/ -}}
+{{- $type := .Get 0 | default "note" -}}
+<aside data-callout="{{ $type }}">
+  {{ .Inner | markdownify }}
+</aside>