Quickstart nextjs

[bradleyshep]

Description of Changes

Adds a new Next.js quickstart template and documentation.

New Template (templates/nextjs-ts/):

• Next.js 15 App Router with TypeScript SpacetimeDB module
• Pre-configured SpacetimeDBProvider with client-side connection handling
• Environment variable support (NEXT_PUBLIC_SPACETIMEDB_HOST, NEXT_PUBLIC_SPACETIMEDB_DB_NAME)
• SSR-safe implementation with "use client" directives
• Example page demonstrating useTable and useReducer hooks
• Dev server runs on port 3001 to avoid conflict with SpacetimeDB on port 3000
• Pre-generated module bindings included

New Documentation (docs/.../00200-nextjs.md):

• 8-step quickstart consistent with other quickstarts (React, TypeScript, Rust, C#)
• Covers: project creation, structure, tables/reducers, CLI testing
• Next.js-specific: provider pattern, SSR considerations, env var configuration, React hooks usage

Updated templates-list.json:

• Added nextjs-ts to highlights and templates list

API and ABI breaking changes

None.

Expected complexity level and risk

1 - Adds a new template and docs without modifying existing functionality.

Testing

• Run spacetime dev --template nextjs-ts my-test-app and verify the app starts
• Navigate to http://localhost:3001 and confirm the UI loads and connects
• Add a person via the UI and verify it appears in the list
• Verify env vars work: set NEXT_PUBLIC_SPACETIMEDB_URI and NEXT_PUBLIC_SPACETIMEDB_MODULE
• Verify the quickstart doc renders correctly in the docs site
• Confirm Next.js appears in the sidebar after React