Replace mock login status with API integration

[zigzagdev]

Description

• Implemented actual API call to check login status.
• Removed all mock logic related to login state.
• Updated context/provider to handle real responses.
• Ensured fallback behaviour on invalid/expired tokens.

[Copilot]

Pull Request Overview

This PR replaces mock authentication logic with real API integration for user login status verification. The changes implement proper token-based authentication using localStorage and centralize API endpoint configuration.

• Removed hardcoded mock user data and replaced it with actual API calls to fetch user profiles
• Added centralized API endpoint configuration with environment variable support
• Enhanced error handling and token cleanup for authentication failures

Reviewed Changes

Copilot reviewed 2 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/context/AuthContext.tsx	Replaced mock authentication logic with real API calls using token validation
src/constants/env.ts	Added centralized API endpoint configuration with environment variable support

[Copilot]

The comment contains Japanese text ('通常のAPI logout'). Consider using English for consistency with the rest of the codebase, such as '// Standard API logout'.

Suggested change

	await logoutUser(); // 通常のAPI logout
	await logoutUser(); // Standard API logout

[Copilot]

[nitpick] Missing space after colon in the object property. Should be 'list: (id: string) =>' for consistent formatting.

Suggested change

	list:(id: string) => `${API_BASE_URL}/users/${id}/posts`,
	list: (id: string) => `${API_BASE_URL}/users/${id}/posts`,

[Copilot]

Logging the full error object may expose sensitive information in production. Consider logging only the error message or a sanitized version of the error.

Suggested change

	console.error('Failed to fetch user profile:', error);
	console.error('Failed to fetch user profile:', error instanceof Error ? error.message : String(error));