Migrate documentation from Antora to Hugo

Migrate the Morphia documentation build system from Antora to Hugo, converting all AsciiDoc content to Markdown.

Custom layouts (base, single, list, header, footer, sidebar) — no theme dependency
Shortcodes for notice/callout blocks (note, warning, tip, important)
Self-contained CSS with responsive layout
Navigation menu defined in data/menu.yaml
Makefile for build, serve, and clean targets

Convert all pages from docs/modules/ROOT/pages/ (.adoc) to docs/content/ (.md):

Getting started: quicktour, migrating, configuration
Features: mapping, queries, updates, deletes, aggregations, indexing, transactions, references, lifecycle-methods, schema-validation, kotlin, text-search, sharding
Support section

AsciiDoc	Markdown/Hugo
`==`, `===` headings	`##`, `###`
`[source,java] ----` code blocks	Fenced ```java blocks
`xref:page.adoc` cross-references	Relative paths (`/features/page/`)
`[NOTE]`, `[WARNING]` admonitions	`{{% notice type %}}` shortcodes
Javadoc links	Normalized to `/javadoc/` prefix

make build  # Production build with minification
make serve  # Local dev server with live reload
make clean  # Remove generated files

Before: Antora toolchain with Ruby dependencies
After: Single Hugo binary

Description