Add SSR-safe SvelteKit todo example

[ayushsri-dev]

This PR adds a robust SvelteKit + ZerithDB example application demonstrating browser-safe database initialization, SSR-safe SDK loading, IndexedDB persistence, and reactive CRUD operations.

Issue #83

The example showcases the recommended integration pattern for using ZerithDB inside SvelteKit applications, including:

• browser-only initialization using SvelteKit's browser environment checks
• dynamic SDK imports to avoid SSR runtime issues
• lightweight browser polyfills required by ZerithDB networking dependencies
• a clean service-layer abstraction for CRUD operations
• scoped and global styling separation
• a documented local-first todo application example

Fixes #

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Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🚀 Performance improvement

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Checklist

• My code follows the style guidelines of this project (pnpm format:check, pnpm lint)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (pnpm test)
• New and existing unit tests pass locally with my changes
• I have run pnpm changeset if my change affects published packages

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Additional Context

This example was designed to serve as a reference implementation for integrating ZerithDB with SvelteKit while maintaining SSR compatibility and local-first persistence behavior.

The app demonstrates:

• task creation
• task updates
• task deletion
• IndexedDB persistence across refreshes
• reactive UI state with Svelte 5 runes