Fix: Add Filament v4 navigation property type declarations

[yassersebai]

• Add union types for navigationGroup and navigationIcon
• Maintains backward compatibility
• Fixes PHP Fatal Error when setting navigation properties
• Tested with Laravel 11 + Filament v4

[Copilot]

Pull Request Overview

This PR adds type declarations for navigation properties to fix compatibility issues with Filament v4. The changes prevent PHP Fatal Errors when setting navigation properties by adding proper union type declarations.

• Adds union type declarations for navigationGroup and navigationIcon properties
• Maintains backward compatibility with null defaults
• Includes additional navigation property declarations for completeness

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[Copilot]

The type declaration uses \BackedEnum but typically Filament v4 navigation icons accept string or classes implementing specific icon interfaces. Consider verifying if \BackedEnum is the correct type for navigationIcon or if it should be a more specific interface.

Suggested change

	protected static string|\BackedEnum|null $navigationIcon = null;
	protected static string|null $navigationIcon = null;

[ManukMinasyan]

@yassersebai Hello, thank you for the PR. How can I reproduce that bug?

[yassersebai]

Steps to Reproduce

1. Create a new page extending BoardPage a long with navigation headers:

<?php

namespace App\Filament\Pages;

use Relaticle\Flowforge\BoardPage;
use Relaticle\Flowforge\Board;

class MyKanbanPage extends BoardPage
{
    protected static ?string $navigationIcon = 'heroicon-o-view-columns';
    protected static ?string $navigationLabel = 'My Kanban Board';
    protected static ?string $navigationGroup = "Operations";
    
    public function board(Board $board): Board
    {
        return $board
            ->query(MyModel::query())
            ->recordTitleAttribute('title')
            ->columnIdentifier('status')
            ->positionIdentifier('position')
            ->columns([
                Column::make('pending')->label('Pending'),
                Column::make('active')->label('Active'),
            ]);
    }
}

2. Register the page in a Filament panel
3. Access the application
4. Fatal error occurs due to type mismatch

[ManukMinasyan]

@yassersebai – For Filament V4, this is the correct way to configure navigation:
https://filamentphp.com/docs/4.x/navigation/overview#grouping-navigation-items

protected static string|BackedEnum|null $navigationIcon = null;
protected static string|UnitEnum|null $navigationGroup = null;
protected static ?string $navigationLabel = null;

No need to redeclare the same properties inside the board page. Please share your full error.