[BUG] Centralize localStorage access to prevent SSR hydration errors and improve type safety

[abhijit9040]

Description

Currently, localStorage is accessed directly passing string literals (e.g., localStorage.getItem("cart")) in over 20+ locations across the codebase (including checkout-card.tsx, nostr-context-provider.tsx, storefront-layout.tsx, etc.).

This architectural pattern introduces a few risks:

• SSR Hydration Risks: Many of these calls lack a typeof window !== "undefined" guard. Directly reading from the window object during Next.js Server-Side Rendering (SSR) causes hydration mismatches or server crashes.
• Key Fragmentation: Because keys like "cart", "tokens", or "sf_seller_pubkey" are magic strings scattered across files, they are prone to typos, making debug sessions difficult and creating silent state failures.
• Boilerplate JSON Logic: Components are constantly reimplementing JSON.parse and JSON.stringify logic, without consistent try/catch fallbacks if the storage data gets corrupted.

Current Behavior

• localStorage.getItem(...) and localStorage.setItem(...) are called directly inside React functional components and hooks.
• String literals are hardcoded across multiple files for the same storage keys.
• Components manually parse JSON without centralized fallback logic or error warning systems.

Expected Behavior

• All localStorage interactions should pipe through a centralized StorageManager utility.
• A strongly-typed STORAGE_KEYS object should act as the single source of truth for all storage keys to prevent typos.
• The wrapper utility should automatically check for the browser environment (typeof window !== "undefined") before attempting to access localStorage, ensuring SSR safety.
• JSON.parse and JSON.stringify logic should be abstracted into safe wrapper definitions with default boundaries.

Steps to Reproduce

1. Open the repository locally and navigate to components/utility-components/checkout-card.tsx or utils/nostr/nostr-helper-functions.ts.
2. Search for the term localStorage.getItem.
3. Note the inconsistent usage of typeof window !== "undefined" guards and the repeated .setItem("cart", JSON.stringify(...)) logic.

Next.js Version

18.17.0

Operating System

Windows 10

Node.js Version

16.2.3

Browser

Chrome

Screenshots

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Additional Context

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Code of Conduct

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