Documentation and Examples Expansion

[rawbytedev]

Overview: Expand and enrich documentation, examples, and tutorials to support users and highlight real-world use cases.

Tasks

• Expand examples/ with CRUD, backend switching, error handling, batch/transactions, key versioning, caching, session storage, config demos
• Add backend comparison table with tradeoffs
• Document all sync/durability guarantees
• Add troubleshooting section
• Include performance characteristics and benchmarks
• Complete all placeholders in IMPLEMENTATION.md
• Add context cancellation and iterator resource management examples