feat(website): quickstart graph example, snippet variants, and comparison updates

[zantvoort]

Summary

Quickstart

• Retitled to "Zero to Storm / in 5 minutes." and reworked the example to show the entity graph: two linked entities (Director, Movie with @FK), multiple inserts, and a query across the relation (Movie_.director.name like "Chris%"), with the generated single-statement join visible via Show SQL
• Setup now leads with the Gradle build; the Storm CLI one-liner (AI-assisted setup) follows as a secondary suggestion, with a note that it runs from the workspace root
• Closing row pairs "Build a real app" with a star link

Snippet variants and copy buttons

• editor() in the shared tutorial theme gains a title-bar variant selector and a Copy button (copy text derived from the highlighted code, so snippets and clipboard content cannot drift)
• Install snippets selectable per Kotlin line (2.0–2.4, matching KSP and storm-compiler-plugin versions; shared KOTLIN_VARIANTS)
• DDL selectable per database: H2, PostgreSQL, MySQL/MariaDB, Oracle, SQL Server, SQLite (shared DATABASE_VARIANTS); fixes the previous script's MySQL-only AUTO_INCREMENT, which H2 2.x rejects outside compatibility modes, and gives MySQL its required table-level FOREIGN KEY
• Applied on the quickstart and the build-a-REST-API tutorial

Landing page

• Hero gets a button row: a gradient "Try it in 5 minutes" primary linking to the quickstart and a secondary linking to the comparison; tightened phone layout
• All GitHub links across the site open in a new tab (rel="noopener")

Build-a-REST-API tutorial

• Routes use repository<>() consistently: new one-line FolderRepository, insertAndFetch for the create path

Comparison

• Website matrix: new rows for session state, deferred loading, standalone transactions, row mapping, and query across relations (effort-focused wording, competitors credited where they have an answer); Jimmer covered in the framework cards instead of the matrix; Storm column highlighted with the brand gradient
• Docs comparison (current and 1.12.0): session state and query-across-relations rows added; "SQL Templates" row renamed to "SQL / SQL templates" and now credits each framework's raw SQL support

Test plan

• npm run build passes; all pages verified rendering on a local docusaurus serve (landing, quickstart, comparison, tutorial, /docs/comparison, /docs/next/comparison)
• Verified variant selectors switch panes and the Copy button follows the selected variant