feat: add non-destructive cache hydration support via isInitialHydrat…

[zto-sbenning]

…ion context

• Add SetContext type with isInitialHydration flag
• Update Handler interface to accept optional SetContext in set()
• Implement NX behavior in redis-strings handler when isInitialHydration is true
• Update all handlers (local-lru, composite) to accept ctx parameter
• Propagate isInitialHydration flag from registerInitialCache to handlers
• Prevents runtime cache overwrites during app restarts and horizontal scaling

Addresses #23

[zto-sbenning]

Hi @AyronK,

I've implemented a solution for #23 . I'd really appreciate your thoughts on this implementation before marking it as ready for review.

Approach chosen

Instead of adding the option to registerInitialCache settings (as initially suggested), I followed your comment about preferring "config on redis handler or env variable" by implementing this at the handler level:

• Added a new SetContext type with an isInitialHydration flag
• Updated the Handler interface to accept optional context in set()
• registerInitialCache passes isInitialHydration: true when hydrating
• Redis handler uses NX option when this flag is set
• All handlers updated to accept the context (backward compatible)

Happy to adjust anything - just wanted to get your feedback on the architecture first!