feat(boilerplate-vite): router integration, docs, and middleware cookbook

[advl]

Done

• Full router demo with SSR, hydration, domain-colocated routes
• wrapper() + group() composition with publicLayout wrapper
• withAuth middleware with typed RouteMiddleware return
• declare module augmentation for generic-free typed routing
• Single RouterProvider wrapping the entire tree
• No @ts-nocheck, no as any casts
• ROUTER_API.md reference with corrected signatures, content.preload, a11y exports
• README with module augmentation guidance
• Middleware cookbook with type-safe examples
• TanStack Router migration guide

Depends on #602

QA

• bun run --filter @canonical/react-boilerplate-vite test — 10 tests pass
• npx tsc --noEmit --project apps/react/boilerplate-vite/tsconfig.json — no type errors
• Verify cd apps/react/boilerplate-vite && bun run dev runs

PR readiness check

• PR should have one of the following labels: Feature 🎁
• PR title follows the Conventional Commits format.
• The code follows the appropriate code standards
• All packages define the required scripts in package.json