fix(app): handle localStorage SecurityError gracefully

[antontranelis]

Summary

• Fixed endless loading screen when localStorage/cookies are unavailable
• Added comprehensive localStorage error handling across the entire codebase
• Implemented graceful fallback to memory-only authentication storage
• Created reusable safeLocalStorage utility for consistent error handling

Changes Made

• ✅ Added try-catch blocks around localStorage access in authLocalStorage
• ✅ Modified getToken() to return null instead of throwing errors
• ✅ Updated auth context to handle missing tokens gracefully
• ✅ NEW: Created safeLocalStorage utility for consistent error handling
• ✅ NEW: Fixed localStorage errors in useTheme hook
• ✅ NEW: Fixed localStorage errors in ThemeControl component
• ✅ Added proper error logging with console.warn
• ✅ Fixed ESLint issues (nullish coalescing, catch-all rules)

Test Plan

• Code passes ESLint with zero warnings
• Authentication flow gracefully handles localStorage unavailability
• Theme functionality works without localStorage access
• App initializes properly even when localStorage throws SecurityError
• Library builds successfully with new utility
• Manual testing in private browsing mode
• Manual testing with strict privacy settings

Technical Details

The issue occurred because localStorage.getItem() throws a SecurityError in certain browser environments (private browsing, strict privacy settings, iframes with cross-origin restrictions). This affected multiple parts of the application:

1. Authentication system: Caused endless loading when trying to retrieve auth tokens
2. Theme system: Could break theme persistence and selection

The fix implements a comprehensive solution:

• Centralized error handling via safeLocalStorage utility
• Graceful degradation to memory-only mode when persistent storage is unavailable
• Consistent error logging for debugging purposes
• No functionality loss - all features work without localStorage

This ensures the app functions correctly across all browser environments and privacy settings.

Fixes #212

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