feat: Add company association to projects with role management

- Created Company model and migration with fields: name, tax_id, address, phone, email, website, type, notes
- Created company_project pivot table with role_in_project field
- Added relationships: Project.companies() and Company.projects()
- Created Livewire component ProjectCompanies for managing company assignments
- Added 'Companies' tab to project edit interface alongside Phases and Users tabs
- Implemented assign/remove company functionality with role selection
- Applied same permissions logic as user assignment (assign users permission or Admin role)

app/Models/Company.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Company extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'name',
+        'tax_id',
+        'address',
+        'phone',
+        'email',
+        'website',
+        'type',
+        'notes',
+    ];
+
+    protected $dates = ['deleted_at'];
+
+    // Relationships
+    public function projects()
+    {
+        return $this->belongsToMany(Project::class, 'company_project')
+                    ->withPivot('role_in_project')
+                    ->withTimestamps();
+    }
+}