fix: Add authentication support for Dedicated HTTP configuration

[arifulhoque7]

Problem

Authentication was not working with the Dedicated HTTP configuration (mcp:serve --transport=http). The Auth::user() method returned null in tool handlers, while HTTP Integrated mode worked fine.

Root Cause

The Dedicated HTTP transport runs independently of Laravel's HTTP kernel and middleware stack, so authentication context was not available to MCP tools.

Solution

This PR implements a comprehensive authentication bridge that:

• ✅ Captures authentication context from HTTP requests
• ✅ Stores context in thread-safe storage
• ✅ Provides Laravel-style facade for accessing auth data
• ✅ Works with both HTTP transport modes
• ✅ Supports all authentication guards (Sanctum, API, Web)
• ✅ Zero breaking changes

Usage

use PhpMcp\Laravel\Facades\McpAuth;

Mcp::tool('get_me', function () {
    return McpAuth::user() ?? Auth::user();
});

Testing

• ✅ Comprehensive test suite included
• ✅ All authentication scenarios covered
• ✅ Backward compatibility verified

Fixes #35