⚡️ Feat: add persistence to notes store

[gndx]

Summary

This PR adds persistence to the notes store by introducing a new createPersistentNotesStore implementation that automatically synchronizes notes with localStorage.

Changes

• Added a persistent notes store that loads initial state from storage.
• Persisted notes on create, update, and delete operations.
• Preserved the existing store API (CRUD, search, ordering, favorites, count).
• Ensured state encapsulation using closures and defensive copies.
• Automatically derived title and excerpt when note content changes.

Motivation

Persisting notes allows the application to retain user data across browser sessions without requiring a backend or external dependencies, improving user experience and reliability.

Impact

• No breaking changes to the public API.
• Existing consumers can adopt persistence by switching to the new store factory.

Notes

• Persistence is implemented using localStorage.
• Storage is updated immediately after every state mutation.