Wojciech mat/token persistance

[WojciechMat]

JWT Token Persistence with localStorage

Problem: Users were logged out after every page refresh because JWT tokens were only stored in memory.

Solution:

• Added localStorage support to persist JWT tokens across browser sessions
• Implemented automatic token validation and expiry checking on app initialization
• Enhanced AuthService to load stored tokens on startup and clear expired tokens
• Added web-only conditional imports to support localStorage functionality

Key Changes:

• AuthService: Added token persistence methods with automatic loading/clearing
• ApiClient: Enhanced to use stored tokens and sync with localStorage
• UserModel: Added UserModel class and UserRole enum
• main.dart: Added initialization flow to wait for token loading
• jwt_decoder.dart: Added token expiry validation utilities

Benefits:

• Users stay logged in after page refresh
• Automatic cleanup of expired tokens
• Better user experience with persistent authentication
• Web-safe implementation with fallback for non-web platforms